can I play this game with the regular 360 controller?

Yes, because they have a standalone version - and you will be able to buy instruments later - like Feb. 2008.

Another question for rockband... How similar is the guitar play to guitar hero? Pretty much identical gameplay or is it different? I thought guitar hero had a patent on that type of gameplay or something.

With that said, I watched a guy playing the drums on demo kiosk at Best Buy. He was playing on hard (or so he said) and the "markers" or whatever they are called were flying by at a fairly aggressive speed and there were A LOT of them. He got through it but was really struggling. It looked fun but really HARD....

 I played it yesterday at Best Buy. I suck hard at Guitar Hero, but was actually pretty good at with the guitar in Rock Band. Finished two songs on Hard on my first try for each. Even got 86% of the notes on the second one. Now my sister, who kicks ass at Guitar Hero, struggled on Rockband. She thought it was a lot harder. Maybe she's just used to the GH controller, I don't know. I liked the Rockband Guitar a lot more than the previous 3 GH Guitars I've tried. Buttons felt a little smaller and quicker to press, and I think it just looked nicer overall. I like the square notes as well, easier to know when they cross the threshold to be hit.

As for the drums, the sticks were missing, so we couldn't really play them. The Kick Pedal also wasn't there, and 
there was no where to sit down. So can't really comment on them. 

ok thanks for your answers. I live in Argentina, and I can't afford to buy the rock band package, that cost more than 600 dollars here

with the 360 controller you only can sing, you can't play the guitar, the bass or the drums.
Confirmed.

The guitar in RockBand is sweet - two places to hit the keys one for normal and another position for solo.
The drum set works well
I'm loving it.
Guitar play might be easier but drum's tough.