I just updated my Sony PSP with firmware update 5.01 and now I have access to the Playstation online store!
It's seems version 5.00 actually gave users access to the online store, I must have missed that update. 5.01 addresses issues with larger memory cards.
It seems quite good, free game demos and you can purchase PSP and PS One classic game titles. Movie and game trailers, wall papers and themes.
I might buy a few new games from the online store, as for someone like me who lives in the middle of nowhere, it's not like I can just pop to the shop and buy new game titles off the shelf.
The sign up process was a bit long winded and required me to submit allot of personal information such as DOB and postal address etc. But the sign up went smoothly and I had no problems accessing the store after the sign up process had completed.