I bought the Master Assassin Edition for 360 which came with the code you get for pre-ordering (Palazzo Medici), as well as another code for the Santa Maria Dei Frari building.
To be honest, you really aren't missing that much by not having access to either building. The only thing you get from it is a little more exploration and some regular Florin treasures I believe.
The maps themselves weren't worth the extra coin, but I do like the Ezio statue and artbook. I'll probably watch the bonus making of DVD sometime. It also has the soundtrack which might be worth a listen.
I beat the game...it took me around 25 hours I think. It took a while for the game's story to really get going, but once it did it was an awesome game.