I played for some while with VHD installed Windows 7 and I enjoyed. After few boots I even selected it to be default. There were some small issues, but biggest one was unfortunate choice of .vhd medium. Booting was slow (few minutes).
Last night I installed Windows 7 on my first partition, overwriting Windows Vista, and thus making it my only boot choice. I do hope that I won't be sorry for this decision.
Big change when compared with .vhd booting? Yes - I am back in sub-minute boot range.