It can improve many things, from not only bug fixes, but also optimization that have been made. For example, web browsing can be improve due to the fixes that were made to the DNS Relay functions. It was implemented improperly, and can even time out.
The biggest issues that were easily resolved were related to HW NAT. With this custom firmware all VPN passthroughs function without the disabling of HW NAT, and including multicasting for wireless. WOL functions now, Ethernet configurations have been added to allow better mixed 10/100 with 1Gb connections, the kernel was compile with MIPS32 optimizations-making it leaner (less memory used) and a bit faster overall, extra funtions are added with robust configuration to the user, etc. The list goes on. Matter of fact version 8 has been released here are the fixes over-all:
ASUS RT-N56U custom firmware 1.0.1.7f-p8 from Padavan
Changes from original firmware 1.0.1.7f:
- Build optimization for MIPS32 (code more fast and smaller).
- Added full support for Optware (start/stop scripts is embedded).
- Added NFS server v3 with WebGUI control. NTFS/FAT32/EXT2/EXT3 exports supported.
- Added SSH server (dropbear-0.52) with WebGUI control. SSH access from WAN supported.
- Added ability to WAN/USB Modem/Routes settings changes without router reboot.
- Added fast WAN source switching to USB Modem without router reboot.
- Added ability for VLAN filtering Internet/IPTV/VoIP without create LAN-WAN bridges.
- Fixed DHCP client for PPPoE WAN connection. PPPoE Dual Access now worked perfectly.
- Fixed L2TP WAN connection in auto mode. VPN heart-beat server now resolved by name.
- Fixed Dual Access PPTP WAN auto-reconnection after broken PPP tunnel (DNS bug).
- Fixed missing NAT MASQUERADE for physical WAN interface, when WAN IP and routes is static.
- Fixed broken IPTV after physical WAN interface new lease obtained (by DHCP).
- Fixed loading more instances of L2TP daemon.
- Fixed more zombie for "pppd" process and others.
- Fixed LAN DHCP server bug (no leases) when DHCP pool end address < xxx.xxx.xxx.11.
- Fixed earlier physical WAN interface up on router startup (spoofing issue).
- Fixed iptables filter rules for port forwarding on router's LAN IP via VirtualServer.
- Fixed casual DNS Relay dead.
- Fixed DNS Relay logic for reverse lookup requests for local IP's. Now all this requests fast
forwarded from LAN DHCP leases, without requesting from WAN ISP DNS.
- Fixed work IPTV UDP-HTTP Proxy with disabled setting "Enable multicast routing". Now udpxy work
without igmpproxy.
- Fixed broken HW_NAT after enabled WiFi "Multicast rate".
- Fixed broken HW_NAT after enabled "L2TP Passthrough" and "IPSec Passthrough".
- Fixed "MAN" static routes loading after disabled static route.
- Both WiFi "Multicast rate" now enabled by default (HTMIX mode).
- Added WiFi 2.4GHz legacy "Multicast rate" modes.
- Added independent IGMP Snooping control for WiFi. Now WiFi IGMP Snooping enabled by default
and dropped all outside multicast traffic.
- Added ability for WiFi region change from WebGUI.
- Fixed WiFi scheduler stupid time overlap check.
- Fixed Telnet server start/stop issues.
- Fixed local network scanner background utility.
- Fixed UPnP Mediaserver force rescan after startup (minidlna new switch "-U" instead of "-R").
- Fixed all Russia timezones.
- Fixed some Russian resources for WebGUI.
- Fixed Samba write issue from MacOS clients.
- Fixed broken setting "No Encryption" for WAN PPTP property.
- Added ability for rebind WPS button actions (short and long press). 8 custom actions is allowed
(e.g. WiFi radio on/off, safe removal USB, reboot, etc).
- Added ability to manual settings physical WAN Ethernet link.
- Added advanced settings for Ethernet switch.
- Added second manual DNS IP for DHCP server.
- Added ability to change source media path for UPnP and iTunes Mediaservers.
- Added fdisk (busybox applet) for partitioning drives from Telnet console.
- Added mke2fs (mkfs.ext2, mkfs.ext3) for making EXT2/EXT3 partitions from Telnet/SSH console.
- Added several Linux utils (such as dd, env, blkid, ip, sysctl, more, ...).
- Added terminfo database for correct terminal keys handling (e.g. for MC). xterm by default.
- Added USB modem ZTE-MF180.
- Added output second (physical) WAN IP address in WebGUI (WAN status).
- Added output MAC address as text in WebGUI (LAN clients table).
- Added physical WAN Ethernet link info in WebGUI (WAN status).
- Added USB HDD spindown after safely remove from WebGUI.
- Added firmware subversion info to WebGUI.
- Updated kernel module Ralink raeth (RT3662 wired GMAC/GMAC2). Increased TX/RX ring buffers up to 512
(tx_ring_full workaround).
- Updated kernel module Ralink Ralink RT3090_ap (WiFi 2.4 GHz). Added WiFi MAC verification to syslog.
- Updated kernel module Ralink Ralink rt2860v2_ap (WiFi 5 GHz). Added WiFi MAC verification to syslog.
- Update all USB subsystem and drivers in Linux kernel.
- Updated busybox to v1.19.3
- Updated pppoe-relay to v3.10.
- Updated igmpproxy to v0.1-stable.
- Updated udpxy to v1.0-21.1.
- Disabled self-reboot after CPU overload.
- Disabled buggy Web redirect page (after internet connection lost).
- Disabled buggy WAN speed auto measurement after WAN up.
- Deleted some national resources (needed more space in NOR Flash).
Changes from previous firmware 1.0.1.7f-p7:
- Added some new WPS button actions.
- Added ability for WiFi region change from WebGUI.
- Added USB HDD spindown after safely remove from WebGUI.
- Added auto changing home dir on optware start/stop.
- Added ssh client into dropbear. Now dropbear used path /opt/libexec/sftp-server for external sftp.
- Added Flow Control option (Ethernet switch) for each port.
- Updated kernel module Ralink raeth (RT3662 wired GMAC/GMAC2).
- Increased TX/RX ring buffers up to 512 for Ralink raeth module (tx_ring_full workaround).
- Updated kernel module Ralink Ralink RT3090_ap (WiFi 2.4 GHz). Added WiFi MAC verification to syslog.
- Updated kernel module Ralink Ralink rt2860v2_ap (WiFi 5 GHz). Added WiFi MAC verification to syslog.
- Update all USB subsystem and drivers in Linux kernel.
- Updated busybox to v1.19.3
- Fixed disabled WiFi WMM combobox on AP in Auto mode.
- Fixed Samba write issue from MacOS clients.
- Fixed broken setting "No Encryption" for WAN PPTP property.
The only negative is the fact that you need to reset the router and perform the configurations again (do not restore any backups from previous firmware), which is not much and not many to make. After such you will not need to perform this again; just flash the firmware is all that is required. But overall it is your router, and how you handle it is his prerogative. One thing to note your "packet aggregation" issue can be a common problem when configuring wireless bridges. Not all wireless chips, even though they may be IEEE compliant, are not fully compatible with particular functions or just the functioning part itself with other vendor's chips.
Honestly, it is good that you have not had the tx_ring_full issue with your network. If you ever do, this firmware can work around it by increasing the descriptor buffers. You do not see Asus fixing any of these really horrible bugs-this really is the issue, and why I would rather prefer custom firmware.
http://code.google.com/p/rt-n56u/downloads/detail?name=RT-N56U_1.0.1.7f-p8-mips32.zip#makechanges