Geez, what a load this bunch is shoveling... So why is Apple under any obligation to a release date beyond 'Spring' in mid March? And yes, in the US, Spring is counted as ending on the solstice, 18:06UT on June 21 this year. Spaces is the only new feature in Leopard? (Time Machine? LDAP throughout? accessibility? iCal server? Core Animation? screen sharing in iChat?) Mac Pro was the only new thing at WWDC last year? (Intel XServe?) Leopard works great on older hardware (Core Solo mini anyone?) and it's not even optimized yet. Not sure what specs you've been reading, but it's been standard (and remains so with Leopard) that each iteration of OS X runs faster, not slower, than the one before on existing hardware. I have a Cube and an original form-factor iMac that run Tiger smooth as silk.
If you don't have something informed and useful to say, it really would be best to avoid contributing. Blathering does us all a disservice.
WWDC June 2007 — What Should We Expect?