You can view most pages using the Treo 650. Speed is dependant on the network you are on...Sprint vs Cingular. I'm sure there are differences in both, but I have not seen anything documented. It takes a good 30-40 seconds to load a page that's filled with graphics. There are different browsers for the 650 and I've heard Xiino is the fastest of the bunch. I use Blazer and it's speed is fine. What type of pages are you looking to load and what are your speed demands?
As always, PDA based sites such as
treomobile.com are still the way to go..
If you're sole reason for buying the Treo 650 is web access, then I'm not sure it's for you. What makes the Treo 650 so great is it's ability to do everything...web,email, organize, palm os app's, etc.
Hope this helps...
Good luck with your decision.