Hovus,
To answer your questions, yes I do reimage every time and that is due to experience with issues upgrading via TFTP. I find it to be easier, faster, more reliable, but not as convenient due to being required onsite. Also since you have to do a backup and DB Test, which usually requires an upload then there is no lost time in doing it that way and I have never had an issue with it, ever. We also do a lot of testing to ensure there are no upgrade issues which requires us to be onsite anyway. Sometimes that is combined with the PM so it is two birds with one stone.
Thanks,
TE