I think Asus and QTN probably pushed things a bit too hard on the 87U - most of the complaints are stability oriented, haven't heard of any issues with performance when it's not busy having issues - for many, it might work ok..
The performance is good. I saw a slight increase in range myself versus the RT-AC68U I was previously using, and 5 GHz throughput was nearly identical. Until last month I was still using the RT-AC87U as my main router, despite having 6-7 different ones to chose from. For me, it was the best of the bunch.