Should i get an iPhone? (3g)?

I know there's a sale going on where the 3g iphone is on sale for $50. I REALLLY need a new phone seeing as my at&t xenon phone that i've had for about a year keeps dying on me. ive never had an iphone and i was wondering if they're good phones? Or do they mess up a lot? I'm also debating on getting an otterbox, would that be the best choice? would getting an iphone mess up anything on my plan at all? thanks!