Tiger won't likely be out until late this year, or even possibly early 2005. Basicially Steve will premiere it at WWDC in June, giving developers time to see the new features, and begin writing new programs that can take advantage of them.

Hardware wise, now is a good time to buy an Apple laptop. Both the iBook and Powerbook lines got upgraded, so they won't be upgraded again for probably another 6-9 months.

As for what system, thats a tough call. It really depends on what you want to do with the new system, and how much you can afford. Powerbooks offer better graphics cards, more expandibility via external ports, and higher resolution screens on the 15 and 17 inch models. The iBooks are going to be more affordable, by sacrificing a few things like processor speed and built in wireless. You can add features to the iBook, but it may bring the price close to a Powerbook.

Also take a look at the deals on older model systems and refurbs. Click the Apple store then the Special deals link with the red tag on either the right or left bars (they move it around from time to time). Smalldog also tends to have a decent refurb selection.