If you can afford a spring floor than I would choose this option. I almost went with what Jann chose, but I don't why I changed my mind. I think it's because I wanted dark grey flooring.
I could not afford spring flooring. I chose mats. I couldn't raise my floor that much since my workout area is on the main floor. My flooring was about 1/2" above the main floor with the double layer of mats. I found a transition strip moulding that fixed this problem. You'd never know that the two are different heights. I also wanted this project done ASAP.
To speed things along with less grunting and groaning from my hubby, I helped a lot. I designed, cut 97% of the shelving wood and also painted it. I cut all the subflooring pieces and installed the flooring. I painted the room. He hung and screwed anything that needs to go up or be affixed to a wall.
The colors stripes for the room were pulled from the room across. I wanted some transition between the rooms. French doors will be added later.
I love my floor. It feels great walking barefoot in there. In the past I always worked with my mats on carpeting. I couldn't believe how different the mats feel over a harder surface. I feel that it's much more stable.
Below is a pic.
You can view more here:
http://www.flickr.com/photos/46535578@N08/show/