I'll second the refurb route (getting ready to get the current one myself, and did that with the prior-gen model). There are quite a few "hidden" features on the current software, but they can be enabled while holding down the Option key or using the older utility. Furthermore, I'll agree that they seem to just run and run without issue (other than some sort of catastrophic failure), as opposed to some routers that do need regular power-cycling. Obviously, it's not an AirPort vs. everything else argument (there are plenty of other great competitive products), but it's a good mix of capabilities, reliability, and ease of use, but at the expense of fiddling with every setting or having every feature.
The best analogy is that the AirPort base stations are to most other routers what the iPhone is to most Android phones - simplified and might frustrate some, but still powerful and a nice product if you're willing to play by its rules.
Then again, maybe my analogy is busted since Google's OnHub series seem to have even less features to fiddle with, and are more expensive (well the Asus one) - still a fascinating product.