Well, Snow Leopard will be whatever the brit-smacker equivalent of 29 smackers is, probably about £58 or some other number in Euros (¢) to upgrade on a currently purchased Macbook.
At any rate, they've recently refreshed the Macbook line, and they're always adding cool stuff that makes people go "D'oh! I should have waited!" I've been bitten by this twice. First with a Mac Mini when I did my initial switch when I bought one and they up and released new ones with faster processors, built-in WiFi and Bluetooth, bigger drives, and more RAM. Next time was when I bought a second generation Macbook, and next thing I know they've got LED screens, better graphics cards, more RAM capability, bigger drives, and lower prices. D'oh! Oh well. My Macbook was pretty sweet as it was.
This time I managed to get in right after a recent refresh, and I'll have to say I can't think of how much better they could make the newer Macbook pros from how they are now. They come with everything (well, except that expresscard slot on the 17" behemoth that costs like, what, a kidney?) that you would want. 2xUSB, Firewire 800, mini-dvi display, audio (two separate for input/output on the 15" and up) Superdrive, Mag-Safe, illuminated keyboard, a brilliant LED lit screen, unibody aluminum case, glass no-button gesture trackpad, 7 hour battery, and built-in iSight camera. The SD card slot is great for me since I have a DSLR (Nikon) that uses SD so I can just pop it out and pop it in the Macbook. Plus you can boot from the SD card if you are so inclined. Oh and this puppy can take up to 8Gig of RAM should I choose to refinance my wife or something to buy it. In the meantime I'll stick with the 4GB it has now.
About the only thing that would make me cry about the next refresh is if they came out with a ...I can't think of anything I'd post on a family board that I'd want so I won't. About the only thing they can do now is drop the price of the 13" to that of a Netbook. Then I might cry. A little bit. Just a little. Otherwise it's brilliant as it is.