Can depend what you are using now.
I had an 80gb vid, and for the first week after i got the touch I was knocked out by it. Then the little limitations started to grate a bit. Mines a 16gb, and that seems really small now. The 8gb would drive me up the wall, but I like to keep a lot of video on mine, if you're not bothered it won't be such an issue.
The touch screen is cool, but it's quite impractical - you have to choose your playlists well because you'll get fed up with having to pull it out of your pocket, slide to unlock and fiddle around to change tracks . . . driving even moreso, it's impossible.
I like the wifi, but again it's not the killer app for me, as my Blackberry can do that, and doesn't need a wifi spot. I jailbroke mine and installed mail - but again the BB trumps it.
I think they're nice gadgets, but for all round awesomeness, I'd have to go with the 80gb g5.