I just bought another Mac, and it came with Leopard. But that's what I wanted. I have some hardware (FW audio interfaces, etc.) that may not get SL support for months so it was important to me to buy before SL was the only OS shipping.
Oh, and I'll still get the up-to-date SL discs for two Macs for the cost of shipping ($9.95/each).
Apple has been pretty good about this sort of thing, though there will always be someone who bought one day earlier than the cutoff. Even still, I can't see that the $29 SL upgrade would be a huge upgrade issue for anyone.
Which FW audio interfaces? I've found the built in support seems decent. Good portion of fw interfaces are based on the cheapie bridgeco chipsets which work fine in SL 32 and 64bit (edirol FA66/100, presonus firebox, maudio firewire *, etc etc). A mates RME Fireface on the other hand only works in 32bit cause RME are yet to issue 64bit kexts. No biggy, SL in 32bit mode seems to be faster than leopard in 32bit anyway.