I fell for the Apple experience back in college.
[That was ummmm,,, +10 years ago

]
Became a convert, and spread the gosple of Macintosh to all.
Convinced family members and friends to buy.
Yet, I never bought one.
Because, for years, and years, and years,,, I waited.
The next best thing was right around the next turn of the calendar.
So, I waited some more.
And, I waited.
But, within the next two weeks, a brand new MB midlevel and a refurbed 24" iMac will be delivered to my humble abode.
Why now, and not before?
Reasons:
1. value for the dollar right now is, IMHO, absolutely great...
2. the capability of these machines [after the shock of Intel-inside semi-wore off], again, is absolutely wonderful...
3. I not only can not wait anymore, I am tired of the PC's I have floating around the house, and the desire to acquire what I want and what I need merged with what is available now...
4. and, lastly, specifically, the MB has the C2D chip and the refurbed 24" iMac C2D is at a price that is very attractive...
As to waiting for Leopard - as others have said, Tiger [from what I have read/seen] is a VERY excellent OS, and should be very capable for quite some time. However, one main thought that I have is to always wait for some time after a new OS is out to let the bugs be shaken out by the masses. My patience for things that go burp in boxes is not very great... especially when I can not proactively fix such by a hammer.
Short version of the above: buy it when you want, when you can, and when the desired item is at a very attractive level; see
https://buyersguide.macrumors.com// 