The grooves are what's more important,  

The only problem with the sole you are referring to is the amount of bounce and shape.  This may or may not be an issue...the bigger issue is the depth of the grooves.  Some tour professionals replace wedges (for free of course) every couple of months or more frequently...however as amateurs we are also not hitting as many balls as they do.  That being said, I would only replace a wedge if the grooves were too worn that I could not spin the ball to my liking or if the sole of the club is so worn that the amount of bounce (or lack of) is affecting my ability to use the club, ie ...it digs too easily in the ground.

Just my two cents...