It looks like it's leaning but after looking at it for a few min, I think that maybe some of the layers are oval (the center ones) and they are placed closer to the right edge. Until the top layer which looks round. I think that is what throws the eye off making it look like it's leaning. I'm pretty sure that the type of baker that Tom Cruise and Katie Holmes would hire to do their cake, would have that baby FLAWLESS or not even bother!
Just my humble opinion...
That cake is definately leaning. I wonder if there were not enough dowels in the bottom layer. The rest look straight to each other, but the right side of the second layer does look like it's leaning into the bottom cake.
The table is way too busy and takes away from the cake. I would get rid of a lot of the roses. I actually do like the design of the cake though.
BTW--were the bride and groom in the picture? I didn't notice. Too busy scrutinizing over the cake. Sign me up for the Cake Decorator's Anonymous meeting. Not that it would help. I'm sure I'd relapse. 
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