Yeah, I think it makes a huge difference. I used to run a PZ31 120x17 with 20mm spacers, but it was a little too low, so stuck a HiFi stem on with the same spacers, and it's great!
You really do NEED to raise the bars up the same amount as the BB rise of the frame (for a good all-round feeling).
Gear ratio seems to benefit from a bit of a tweak too - since the rear ends can 'shoot through' more easily, I found that going from 20-17 to 18-15 (slightly harder) felt loads better (Y)