In my eyes, it's too much of a clone of the Season 4 poster. In fact, it's pretty much exactly the same but without trees and water. The same colour scheme? Come on... And don't get me started on that building. (Although I think the off Island characters look awesome)
However, early reports have indicated there's a lot of big fans already. Let me know what you think in the comments section (but NO SPOILERS), or alternatively discuss it at this thread on the forums (which is in the Spoilers sub-forum, BEWARE, and don't say I didn't warn you for any spoilers in the thread).
P.S. For comparison, here's the posters for Season 1, 2, 3, and 4.