I've used the smiting line... and quite frankly, it's a ton of fun!
The only problem I ever run into is when my teammates suddenly expect me to heal them... dang it, does the bald head make me look like I want to babysit them all day long?
In other words, if you take a primary monk and don't heal (at least initally after release) people will not respect you... partially due to the fact that they don't realize just how powerful some of the smiting line buffs are.
People will eventually get smarter and then it will be socially acceptable to be a smiting monk.
EDIT: Divine Favor is still quite a useful skill line, so being a primary monk actually means that you need to put fewer points into healing. Theoretically, (this isn't completely sound) you can put 4 levels into divine and 4 levels into healing spells which averages your healing power to a fairly decent amount (the exception being DOT heals.) This is substantially cheaper than getting 8 levels of healing on another character for a similiar effect. Will it be uber 100% kind of heals? Probably not, but even then that can be compensated for if you take a pure monk build!