No one's as big of a Monte fan as I am. My very first product, Poisoncraft, was also the first 3pp product with AE conversion notes under Monte's AE license.
Anyone who doubts his ability to make a megadungeon interesting doesn't have Ptolus. I look at this as a way to get in on the next Ptolus from day one, which is an exiciting prospect to say the least.
That said, I'm a full-fledged 4e-phile, so I'll just be checking it out for giggles. To be clear, I simply don't think this can be done for 4e under the GSL. Indeed, it seems like exactly the kind of thing Wizards wants to avoid competing with their DDI.