[Personal stuff] My digital setup has an adjustable active area: I can either work on a 6"x8" area or a larger one like 20"x22"(maybe bigger; but I haven't got the time to test it yet)... and cost me less than 200$ (CDN)! Perfect for the beginner that I am!
I can use it on my LCD, my desk, a laptop, paper, trace my drawings and heck, even draw without a surface (will lack precision, but still useful; sometimes) [End of boast]
Wacom Intuos 4
Now, if you are working as a professional and have the funding, I say go for it! Or any new tools that can make you more productive and advance your art.
If you suck on a bamboo though (or whatever tool you're using), stop dreaming and practice more (and save money).
I don't know about sucking on a bamboo having much to do with it, there's a learning curve with any tablet, but the bamboo seems too small to me and not enough sensitivity to be useful. For painting at least. But you are right that a new expensive tool won't improve your art skills, you have to do that yourself.
As for the Intuos 4, I like the design and the scroll wheel, plus the LED displays, a good way to get someone using shortcut keys is have the special ones you've mapped displayed. Also good if you're learning the shortcuts in a new program. 2048 pressure levels is impressive, but at half that much with the Intuos 3 I haven't had any problems. So for myself I'll hold off on getting another tablet. Actually I'd rather replace it with a Cintiq, if anything.
it looks very awesome, but i think it costs a bit too much. doesn't look quite cool enough for me to buy another tablet. my tablet may not be great, but it works well enough. (acutally, i think most of the problems arise cuz my computer dun like both my tablet and my drawing program open at once...)
I couldn't really justify going from Intuos3 to Intuos4 for how much it would cost; honestly, I don't use the buttons on the tablet, anyway - I'm more comfortable with one hand on the keyboard while I paint. What's left once you take the buttons away from the Intuos4 is double the sensitivity, but do I really need that?
When my Intuos3 breaks is when I'll probably go to Intuos4 - unless I could get a used Intuos3 for half the price.