As I have mentioned many times in this forum, all entry level DSLRs (regardless of brand) is capable to produce good pictures if you use it within it's limitation. Since you have eyed on the A330, I would suggest that you go to the shops to take a look and play with the cam. Not everyone likes the ergonomics of the cam but the cam is pretty good for beginners with it's very user friendly interface. The AF on the live view is superb too. :thumbsup:
Yes, why not? Sony is one of the upcoming brands in the DSLR markets and with their long history in sensor making, it's a very good brand. If you had researched on the history, you would have noticed that Sony had bought over Konica Minolta and build the Alpha line of cams based on the previous Minolta mount. Minolta has a very long history in camera making and they have very good innovations back then.
Having said that, when you buy into the Sony Alphas, you could actually use the old lenses from Minolta (Alpha mount) as well.
Which to choose will depend on yourself cos you are the one using it. So it has to be comfortable in your hands. As I have big hands, I would not consider the EP1. Besides the EP1 does not have a mirror in the body so strictly speaking it's not a DSLR. Also a friend of mine posed a question to me which sets me thinking. He asked me 'imagine mounting a longer zoom lens on the EP1, will it be able to balance?'
As for the D3000, I do not have much comments on that cam, but I believe the AF on the Sony cams are the best so far. It would be better for you to try the cams out.