It's called "CYA." With no 911 capability and the inherent reliability issues, it makes sense for them to make some effort to discourage people from using Skype as their primary phone system.
Regardless, I'm in the process of doing it. Skype is replacing my cell phone, which replaced my home phone years ago. How and why?
Here's how. My approach is a bit more ... interesting. I'm running Skype on my laptop, desktop, and PDA and am establishing a portable wi-fi hotspot using a Sprint Novatel S720 PCMCIA card and the Linksys WRT54G3G-ST router (it directly accepts the PCMCIA card, dials to Sprint's data network, and serves wi-fi). The router will be mounted in the trunk of my car, possibly with a mag-mount wi-fi antenna for better hotspot range, and will of course be portable for indoor use. I chose to use a PDA over a Skype phone for compatibility with commercial hotspots. I'm also using Grand Central as my primary inbound number and have it set to ring a backup cell phone, as well as a SIP number over at Gizmo I'm test-driving. No matter what system I'm using (VoIP or POTS) callers will find me.
You can find more information on my project here:
Your situation may vary, of course.
I did take the precaution of entering the direct-dial numbers for the local PSAP's into my Skype phone list such that they appear at the top of the list. In the event I need quick access in an emergency, the local PSAP numbers are right at the top and I can call them easily. I hope that is never necessary.