El_Gato -he defended it very well vs kron.
"Marcelo, how do I defend the guillotine?" "Don't get there"
MG shows TONS of both positional and submission escapes/defenses, besides advising not to get there. It's one of the best aspects of the site in that you get to see his defense/recovery systems...cuz of course, you don't get to see much of it in competition at all. 
While Marcelo's attitude is not to allow yourself to get too deeply caught in someone's strength, ie. De La Riva, Spider Guard, etc, Marcelo is awesome at showing how you should posture, have grip controls, etc, so it will be difficult for your opponent to get in that position in the first place, or get too deeply into the position.
Likewise, I do recall him teaching specific passes for the De La Riva, Spider Guard, dealing with Reverse De La Riva, etc.
in
the plus side: ull learn MGs game, which suits me well cuz I have a very similar body type.
the negative side: ull only learn his game.
I find this site complements someone well if they are already learning bjj at a gym in a structured manner.
Are people actually surprised that when you go to "MGInAction.com" it features Marcelo Garcia's style of jiu-jitsu?