I agree with most...my main reason is wait until all kinks have been ironed out: Vista is just too new to have a decent choice of fully-compatible programs to choose from.
Further, progamming-wise, some things have been allowed in Vista so that third party apps can initially work in it...with the understanding that meanwhile SP1 is released, coding will be re-compiled...Another uncertainty.....
And Windows firewall has always had a decent rep(after its troubled initial release, that is)., so.....
BTW the following is not a firewall...more like a spyblocker / av-- seems to work seamlessly in Visa:
http://www.novatix.com/Cyberhawk/