[pct-l] GPS for distance

[shon mcganty]

I don't like gadgets and thought I'd never want a GPS, but I really want a good way to determine how many miles I hiked for my trail journals. 
I'm worried that I might drop several hundred dollars on a GPS unit and find that they don't correctly calculate you're distance.  I went down to REI but the employee I asked was not helpful (he admitted to not knowing much).
So I wanted to ask anyone on this list who is knowledgeable about using GPS for distance calculation.  Does it work well?  I live/hike in a heavily forested environment.  Is it common for GPS to loose contact with satellites in forest cover?
I was wondering if a hand held GPS would be more powerful and accurate over a wrist watch GPS.  The REI guy said a hand held unit would be better in the forest only if it was held correctly, with the antenna pointed up at the satellites.  In no way will I be hiking while holding onto a GPS, so it's got to work while stored either on a pack's side pouch or strapped to the top.
Any information would be helpful.  Thank you.