You won't be dissapointed, it's a touch screen smartphone (even more than a smartphone) with a qwerty. IMHO it doesn't lack anything except the speeds that these days dual core and quad core phones can offer, but I still prefer the N900 (that's why I haven't swapped it yet).
You won't have lots of apps and games like the other smartphones with android (you can install android on N900 though, I assume you know this)... If this doesn't bother you, you should get it.