I love MythTv, and have been using it for years and years, but it is absolutely not easy (though I have more obscure hardware, and have never used mythbuntu). I've also tried being a sysadmin for my friends' myth boxes....I would never wish that on anyone. The stability has always been the biggest issue. Random crashes are extroadinarily annoying. With Firewire, I found recording very unreliable, image quality is very dependant on the capture method. But I haven't seem anything that can support my High-Def recording with auto-commercial detection, and for that,I'm willing to stick with it.
I've heard that you can run 'Play On!' in a virtual-machine on windows to convert netflix to upnp streams (which can then be watched on Linux). I haven't tried it myself though. Certainly not ideal, but perhaps viable for those certain use models.
Also Blu-Ray is still really hard in Linux. I've considered a Windows MythTV frontend with a linux backend which might give me the flexibility I want, but I don't think there's a good integrated solution for that.