It depends on your locality as well its better if you tell to which region you belong to. As for South Asia a special promo is running.
no problem in buying windows 7 , we can receive the regular updates , those critical updates will fixes all issues. initially when windows xp released it was with 50% bug , but now people are uninstalling vista and using xp. The same thing will happen in both vista and windows 7
Generally with any new MS OS you should wait until the first SP becomes available. They like to use live sales as their beta program
you will get all the up gradation details or all the tips related to window 7 on the link given below http://windows7.iyogi.net/