I have about 5 titles and haven't had an issue with any of them causing issues or anything. I think if I was seeing regular issues on any disc, that wasn't attributable to a faulty disc, I would take my PS3 back. I got it for Blu-ray playback, and that's what it's giving me.
All for my wasted money price of $600 (got the premium one).
Really, while HD DVD is excellent in quality and has some great titles, there are just going to be more current release movies that I don't already have on DVD coming out for Blu-ray... and that just excites the heck out of me. I imagine I may someday end up with a dual format player or HD DVD player though if Universal doesn't start releasing Blu-ray titles. They have to many great movies to ignore.
For getting the 20GB model: Try CircuitCity.com as they may have a store in your area with them in stock.
EB Games also seems to have them in stock (non bundled) :
http://www.ebgames.com/search.asp?N=141+83