Wow, I can't believe the EXACT same thing happened to someone else.
I actually had this same problem when I bought my PS3 last year around the same time as you. I even made a thread here asking everyone why the heck the download just literally restarted once it finished.
I hooked that sucker in and started downloading the killzone MP from the PS store and I waited in anticipation to play KZ MP, but once it got to 100%, it started downloading again. I was like WTF? So yeah I just left it and it took a LONG time to download the 4GB or whatever size the game was. I was incredibly annoyed at why it took so long, especially given my internet connection is 30Mbps down and anything I download on my 360 is uber fast.
Funny enough, as I started downloading more, the problem just didn't occur again. Now whenever I download something on the PS3, it does it almost as fast, if not just as fast as my 360, which does things incredibly fast. And I really enjoy my PS3 with all the games it has to offer. I almost play it as much as my 360 now even though most of my friends and the majority of my games are on that console.
I think you made a very hasty decision. You shouldn't just return a product from the first quick you see. You need to try several different things before you make such a decision. Anyway hope you don't regret.
