I play for one of the best schools in my DIII conference, and there are definitely a lot of high level players out there. Our team can beat some DII schools, but we're still not considered elite in DIII.
My experience as a whole? I really love it. It helps that I have awesome teammates but there's just something about turning an individual sport into something revolving around a team that is great.
I chose DIII for the academics. Realistically I know I'm a student first and then an athlete. I'm not going to go to some mediocre school for tennis and gamble with my education. With DIII, tennis is a big part of my life still but it isn't the only thing in my life.
Wilson BLX Blade 98 strung with Solinco Tour Bite 16 at 52 lbs. My College Tennis Video: http://www.youtube.com/watch?v=2SfqRalc0V8