I don't 'heard' this or that, I already run Win 7 (32 and 64) from the betas and RCs, and now the finalized product, besides XP and Vista.
( ..... And my beloved W98SE of course ....
)
Rule of thumb is pretty simple:
If you have or will buy recent hardware with at least 2GB RAM Win7 beats all.
4GB RAM or more: Win7-64.
Older (or not so recent single core hardware) with a 1GB RAM: don't bother: stay away from Win7. (And Vista)
Did MS
really had to call it a 'new' OS .....? Kinda doubtful, there are some things improved, but even then, they could have done a major service pack upgrade for Vista users, but yeah, a 'new' OS also means $$$$$$. *sigh*