For those on the fence, the reviews so far say that it's a return to Telltale's usual form of making the best use of the license. The game's method of using dialog choices to influence the outcome of future events in the game is particularly praised, as is the story (as par-for-the course for a Telltale title). It should be noted that there are a lot of action sequences, and that it lacks traditional inventory-based puzzles found in most of Telltale's adventure games, but it's a huge improvement over the gameplay found in Jurassic Park.
The game is not out on Telltale's site yet or on XBLA. It will be out on Telltale's site later today, and on XBLA soon.
Update: Telltale found a server issue that only concerns the build that was intended to be uploaded to the Telltale website. They've been trying to fix the issue all day, but it doesn't appear that they'll be able to fix it tonight. Thankfully, they posted news on their forums that everyone who pre-ordered the game from Telltale's site will be sent Steam codes to their e-mail addresses so they can play the game via Steam (and get the extras like Steam Achievements that go with it).
Update 2 (April 27): It was released yesterday at Telltale's site. It's out now on XBLA as well (and of course, PSN and Steam).