One of the things that pushed towards the Dell 830 and away from the MBP was that I was used to the 1920x1200 rez but liked getting that on a 15" screen. (That and a preference for a clit mouse.)
Bought it with the FreeDOS option, tossed on Kubuntu, and happily hacking away.
If the Dell Studio 15's were compatible with leopard, I'd go with that because there's a 1900x1200 resolution upgrade that is VERY reasonably priced.
If you regularly plug into a bigger screen, a smaller machine might be better. If the Dell isn't compatible yet, I'm sure it will be in the future. Darn hackers!
There just isn't much in the way of progress. The only people out there making any (somewhat) progress is the macvidia team and they're still fundamentally reliant upon Apple's willingness to support a given chip for the Mac Pro.
It's not a matter of time if no one cares.
The problem is that people either already own a mac and don't care about people who can't afford one, or they don't care about using the OS.
I love the hardware, I really really do, but I'm not dumping that kind of money into a machine. It's not feasible on my income (meager).
I had a 15" but couldn't develop on it. Since I got this 17", I've used it 100% of the time, 10+ hours a day.