One of the best top lane and split pusher in the game, due to his utility and build order. With this champion you need to be patient during laning phase and use stand united to save allies or gain assists as you are less likely to get any kill during early game. However once you get the core build item, you will be a big threat that enemy team can not ignore.
For my shen build guide check it on solomid.net
My personal favorite champion for support role. She has strong harass skill and decent heal, if played correctly you can zone out enemy champion from farming. Main challenge for playing her is you need a lot of practice to know how to use her passive and Q for harassing safely.
I noticed that with Magic Penetration Runes and Mastery, you can do around 100-150 damage from her passive and Q to enemy champion at level 5. Combine it with her ultimate and your AD carry damage, you can get a kill without jungler help.
I think she is a little bit overpowered with correct play style. For more details click here for my guide on solomid.net