Funny, I just spent 2-3 hours playing this with my kids Sat night (got it from Amazon Thanksgiving week when it was $19.99).
As for how good it is, well, the games are no mystery - if you like any of those sorts of things it is a good buy. My kids are already fairly tired of it, but it has some single-player appeal (e.g., you can go for high scores in Boggle, and there are 1400 achievement points to track down if you are inclined). The advanced versions of the games provide a little more oomph too. A great example of this is Connect Four - yeah, a pretty boring game by itself, but there's a version where you have pieces that push others off the bottom, crush the ones below them, or explode when you drop them. Throw in a timer and that makes it a whole new game. I had some fun just playing this one against the AI.
FYI, the games are Boggle, Scrabble (no AI play here unfortunately - single player is just you making your own words one after the other), Connect Four, Battleship, Yahtzee, Sorry, and Sorry Sliders. I haven't played Yahtzee since I was a kid so that was kind of fun to play again and the automatic scoring makes it go much quicker (ditto with Scrabble though it is still a slow game by nature).
Given that they try to charge, what, $10 for each of these on XBL (confirmed - even at this moment the Amazon sold codes are $10 each), getting this disc for $20 is a great deal. Even when they have them on sale for $5 (and I think one or two have been already) it is still a good deal. I mean, I've already gotten my $3 worth of entertainment from each of them.
I'll try running the game from the HD as I think I have some trials. There is a note in the case, though, that says you should run it from the disc so I'm guessing it won't work. I actually started it up by accident from the HD and quit before I got to the game menu after I realized what I did - I should have checked it out first. But it certainly didn't complain upon startup. The disc does spin the whole time which can be annoying. Fortunately a beneficial side effect of my RRoD was that I got back a much quieter system so it doesn't bother me as much as it would have a year ago.