I, too, am an Apple fanboy and have been very happy with my various Time Capsules, Airport Extreme, and Airport Expresses. They have always worked very well for me and I have a very mixed environment with a lot of non-Apple equipment accessing them as well.
That being said, I got the bug to upgrade, so thought I would try out the new Linksys WRT 1900 AC wireless router to see what it was like. It was a little rough at first, but now is doing really well. I was always able to connect to it, but oftentimes throughput would be an issue with my Apple equipment on the 2.4 GHz band. I did some research and found that Apple doesn't really play well with wide channels on that band, so I disabled them and all has been good ever since.
The main differences that I've noticed is that I do get better overall throughput with the Linksys than I did with the Time Capsule. It's not night and day, mind you, but maybe about a 15-20% improvement. The range is also a bit better than the Time Capsule, though not as much as I had hoped for. It still wasn't enough to get me an AC signal at the other end of the house, so when Linksys released the RE 8500 range extender recently, I added one of those. It did the trick and I now have AC coverage throughout my home with no additional wires.
I wish that the FCC would allow the 5GHz WiFi signals to broadcast with enough power to give an equivalent range to that of 2.4GHz signals, but, alas, they do not.
Now if I could just get the SP3 to make a good, high-speed connection, I'd be all set.