I saw on the demo version install routine, it actually listed Vegas 5, 6, & 7.
I personally have never had bug issues with Red. I know they had a 3GL update some months ago and that seemed to fix some things. it has performed pretty well for me.
Yes, I also always had to also do the red render before continuing to work in VV as RED would bog down the VV timeline playback when the playhead passes the effect. making it cumbersome overall and only used when absolutly nessisary. red is great....just took alot of effort to get "that effect" Im looking for. if timeline sync were fixed it would really help that.