Personally (at work), we tend to mostly sell HP products. Just have to avoid their entry level throw-after-use products. Their 200-500$ lineup is pretty good, and ink cost is better than you'd expect even on inkjet products. That new product line they introduced a year or two ago has inkjet having a much lower cost per page than a laserjet (new ink technology they were advertising heavily at a recent tradeshow). And the Laserjet 5000 we have at work is over 12 years old, and still going strong.
We used to be heavily Brother-centric. We ourselves used an HL-1660 that was very reliable. Then, Brother quality suddenly dropped in the early 2000s, had a lot of software-related issues with their products, which made us switch to HP. I haven't looked at them recently, it's quite possible that they have improved since then - they're in general a fairly good printer company. They just seemed to have trouble adjusting with the move from 16-bit Win9x to 32-bit WinXP, and with the move to networked printing/scanning/faxing (got a customer burned by the latter - product advertised with networked Fax support, except they didn't mention that this fax support ONLY worked under Win98 - they didn't support it under WinXP...)
We sold a few Epson over the years. Great image quality (we mostly sold them to people wanting photo quality printing), but the recent models we sold had reliability issues. Frequent paper jams after only ~2 years of average use by a customer, they were ready to throw it out of the window when I replaced it last week...
Haven't really dealt with Canon since the early 2000's, except for their bigger ImageClass Business products. Their installation is fairly easy, and customers never complained about them either. I do have a Canon at home, but that's because I got the cheapest printer I could find that came with cartridges - I print maybe 20 pages a year...
My previous HP Deskjet (D2420 or something like that) died after only 2 or 3 years (was one of their cheap, entry level garbage products). The previous HP Deskjet 930C however, lasted for many years. I loved that printer.
Have a few customers with Toshiba business class products, they seem decent, but the driver is sometimes problematic. It's sometimes a guessing game to figure out which driver to use, as a given model can come with a different model of daughterboard, which requires a different driver.
A few other customers with large Konica-Minolta, great products so far (at least I never hear any complaint, and their drivers are fairly easy to deal with).
The only Lexmark models we dealt with were their entry level inkjet, which were horribly noisy - we moved to Canon and HP at the time. Never really worked with their mid range products, so I can't comment on them.
Purely software-wise, I like Canon because they're light. HP's software is a bloated pig eating lots of resources and having stability issues - I usually install a very stripped down setup of their software whenever possible. Epson is somewhere in the middle.
That pretty much covers my experience with the various brands with my customers
