I've been to 2 VGL concerts, both at the Hollywood Bowl (the debut one more than a year ago, then again a few weeks ago). Both times were well worth it. They had a fair amount of glitches and poorly-executed ideas at the first show, but they were ironed out by the second show.
It's a different experience from Play! (which I saw in Chicago). It's not just the orchestra playing; there are video screens which show clips from the games edited together to match the music, like in a movie trailer (it works really well IMO). The stage has a fancy colored light show going on, which isn't distracting, but isn't the sort of thing you would see at a fancier concert. There are also some interactive segments (a contest where someone plays Frogger with the audience playing in tune to his movements), and it's generally more of a fun, family-friendly type of show than Play!, which felt more like a semi-formal night at the symphony.
As for the music, it's more focused on American VGM than Japanese VGM, though they played Metal Gear Solid, Sonic, Mario and Zelda, for example. Also, don't expect much in the way of Final Fantasy: Square was reluctant to give them the rights to FF music, so they're somewhat limited in what they can play. At the first show, they did One-Winged Angel by a solo pianist--think about that for a second. At the last show, they did do One-Winged Angel by the whole orchestra and choir, which was good, but I don't know if that will continue. Also, Square won't let them show any clips from their games, so both segments were entirely without video clips (not like that ruined the music or anything). The same applied to Kingdom Hearts, so to compensate, they instead did a montage of clips from Disney movies. It still worked well IMO.