I've never used one, but Metz has a pretty good reputation.
One point to consider, if you're in the market, is that in most applications the $199 "64 AF-1" is probably not much more powerful than the $150 "57 AF-1" because the 64 achieves the higher Guide Number (GN) in large part because the zoom head goes to 200mm instead of 105mm. I haven't looked up the numbers but i'd bet that from 12-100mm they are pretty similar.
EDIT: Just for kicks, I did find the numbers. Equalized at ISO 100 and 50mm (35mm film) the GN are 43 and 38 (meters) respectively.