I know I'm awfully late to this party, but I just watched the Quiptracks 5th Anniversary Jurassic Park (available on the Quiptracks site). I laughed out loud plenty of times and appreciated the diversity of jokes, from impressions to sophisticated critiques to total groaner puns. It falls just a bit short of the quality of the Rifftrax one, though I may be biased because of my extreme love for Weird Al and my schoolgirl giddiness at hearing him riff with Mike. Since CJones and Darth Geek pretty much covered all my favorite lines in their reviews ages ago, I'll just add that I liked the way they handled the very different absurdities of Weird Al and Jeff Goldblum. My only real complaint was the song at the end which needed some serious editing.
On a personal note, I'm glad to hear that this was an early Quiptracks effort; they got good fast and then got even better; I'd love to emulate that.