I checked it out. There is no commentary! It's just videos of gameplay. I find that to be very boring. If they had included entertaining, or engaging commentary, then i would watch. But not this!
Edit:
On the other hand, as ppl have pointed out here: it might be useful for info on a game you are not sure whether you will enjoy (if there are no Demos), tutorials (if they are limited or nonexistent in the game), or walkthrough's.
The most interesting suggestion is the ability to check out a game even if you do not own the platform it is on, which i just realized is crucial for KH fans like myself who cannot afford to buy all the portable platform just to keep up with the story.
I bought a DS for the purpose of playing Pokemon and KH 358/2 Days, my brother got a PSP to maintain our Playstation support and play KH BBS (so i have been able to check out the game, and watch the video gallery in the game to see the story cutscenes). Neither of us are going to buy a 3DS just so we can play KH 3D, so this seems like a much better solution than just reading about it on KH wiki. Thanks!