I never thought there was much of a 'good time to buy' with technology, especially Apple stuff.
It's so fast moving that whenever you buy, give it 3 months and you'll probably have an old model!
I'm from the UK (I gathered this is a mainly US forum?) and I think that we're lacking behind as well. I mean rumours of when the iPhone is to launch over with you guys (Mid summerish) it's going to be nearer the next winter for us!
If Leopard will be out with you in Spring 07 then will it be with me around then? I hope so.
I'm getting a Mac Book Pro for University in September but wouldn't mind getting it quicker, however I'm in the same situation as you - do I buy now and feed my cravings, or wait until September - and have a possibly better machine.
I don't think that iLife is much of an influence on me, as software is much 'easier' to get hold of then hardware as it were, so the price of that doesn't influence me one bit. It's whether there'll be any major technology upgrades eg Better webcam, LED lit screen etc.
I think that's the whole reason for why I'm on here really. Doing my research!

Nick