I too am hearing stories of the power supplies dying around 17-18 months with the Time Capsules. While the units come with a 12 month warranty, a Mac with AppleCare will extend to cover the Time Capsule for the 3 years. So far the two I've deployed work fine, with the oldest approaching a year old now. If it's anything like the very first Apple Airport I bought in 99, it will probably turn into a cheep fix most resellers can handle in under a day. The sealed nature of the box does bother me though. The Extreme comes with an external power supply and no disk sealed inside, so I'm less concerned there.

As for wireless range, I use an Airport Extreme Dual Band as the main home router, then I have an Airport Express in my room. Both are hooked into the LAN, and this provides excellent 5GHz N coverage for the laptops anywhere in the house. With just the Extreme unit for 2.4 GHz, I still get good enough G coverage for my iPhone across a 1000sf area with 2 walls between them. It would have been fine for 5GHZ as well for normal web and video use, but I wanted the quickest network speeds possible for the Air when it's next to my Mac Pro. Comparing just the Extreme to my two previous routers, it has the best range on both 2.4 and 5GHz bands. The other routers I owned were a Linksys 610N (junk) and a Buffalo dual band router that due to the lawsuit and their laziness has become stuck at an older N spec version that isn't very compatible with modern systems.

At my grandparents house, the Time Capsule sits in the basement near the middle of the house, and provides coverage across both floors and even outside into their yard a decent ways. I can't speak for network speeds there much, but it's enough to carry on stable video chat sessions.

And the one at my moms house sits on the side of the house closest to their neighbor to extend the network. They live in an uncrowded area, so interference isn't an issue, and the extension is enough to cover her older house with strong signal, and provide coverage in her yard as well.