I'm a graphics designer and programmer and I use parallels desktop everyday with Adobe Photoshop CS w/o any problems. With this new "beta" update they released a few days ago, things run even better and smoother. I've completely abandoned my pentium 4 2.8ghz desktop running XP pro for my 2.0ghz Macbook running XP through Parallels. I also use Macromedia Flash 7 MX and it runs fine. I don't have 8 so I can't tell you how well that runs.
As always, BootCamp WILL be faster than running through parallels because native is always better (for the most part) than any virtualized/emulated solution in terms of speed. However, with that said, Parallels runs these programs very, very well.
Be sure to get the max (2 gigs) ram before attempting to use Parallels. I've assigned 1gb to XP.
Good luck!