I have recently gotten a 360 also. I was also a Playstation guy, but paying $600 for a video game system just isn't worth it to me. I think it was worth getting though, I say go for it.
I got the "Core" version. I'm pretty sure you can save your progress on the other version, but you have to buy a memory card. With the Core, all of the memory is in the machine so you don't have to buy a memory card. I think you can play online with both versions also.
Also noticed that the games for 360 are almost $100. Are all games that expensive? A guy could go broke fairly quickly!
Don't know where you saw games for $100, because the highest I've seen is about $60. Not too bad in my opinion.