Think about it. Lets assume the average song is 4 mb, and 3 minutes and a half long. With 30 gigs, that gives you about 18 days of music. Do you really need 18 whole days full of music :-? I took away 2 gigs for applications and whatnot, however having video will give you a lot less space. ( Each film is somewhere near a gigabyte).
Plus, the iTouch and the iPhone are waaaay cooler than an ipod.
You can do infinitely more things, new apps come out every day.
You can browse the internet. It has a bigger screen.
They are all around cooler.
Assuming you can sell your old ipod to a friend or whatever for some decent cash, go for the iTouch.
P.S. I personally have a nano, one of those new ones that come in bright colours. My parents got it for me, so kind of stuck with it :

Whatever, it's pretty cool.