Hi there,
I started training with a personal trainer a year ago because I was diagnosed with Osteopenia and weightbearing excercise is the best thing for it. I has also been going to the gym regulary for many years and felt I needed something new.
I absolutely love it and the results are great but I suppose it depends very much on who you get and what you're into. Mine is very tough, a friend of mine went and she hated it said she did not believe in the no pain no gain philosophy.
If you like going to the gym, working out to a specific routine and don't mind a bit of pain (or a lot if you don't stretch and cool down properly) you will enjoy working out with a personal trainer. You will also see results very quickly because they push you to a level you would never push yourself.
My body shape has changed completely (for the better I like to think) and my bone density has decreased for the first time in 3 years.
It's not cheap (I pay 60 Euro for one session) but I only do 3-4 sessions every 2 or 3 month after I have worked through all my programs.
M.