I think there definitely are some valid downsides to the points discussed, and I'd like to add my own two cents
For impulse buys obviously lower is better and $10 is a pretty good sweet spot. However, the whole thing about LCG's is that, especially with this new release scheme, it doesn't need to be an impulse buy anymore. I would think this more akin to an MMO subscription. It's the same price for the majority of the major ones, and I think because the releases are monthly, people can plan for it just like they would an MMO. It's hard not to relate card game with impulse buy, but there's really no need for it to be impulsive with this format.
Vermillian, I can understand what you're saying about giving common cards to new players, but I think that's less of a concern with this format. There are no CCG's that I can think of where you could buy the core set and a quarter's worth of product for $85 ($40 core plus $15 month with new format). That's a very low barrier for entry compared to most CCG's. Also, that price would be for a color or a faction, etc. This is for a (except for the core set) complete playset. In fact, if I were just inclined to play order and my friend destruction, it seems that the cost for both of us would be $42.50 since the cards are easy to split.
I am the kind of person who wants every deck building option available. I really enjoy building decks and playing different styles to see how they work, so I can't express how much this announcement excites me! I was just keeping up with Invasion, but now for the same price I can keep up with Invasion and AGoT. Martells, here I come.