I think Bard is very underestimated right now and he is a very good support but he takes time to master and to understand his kit. Most people underestimate Bard and don't know how to play against him very well, allowing you to get easy stuns off early kills.

Positioning is a very important part of bards kit, you need to be able to position yourself to stun people and E through walls.

1: When playing as bard remember this 1 golden rule; ALWAYS TELL YOUR ADC WHEN YOU NEED TO GET CHIMES! Leave behind a health shrine for your ADC when you need to get chimes. If you dont tell your ADC you need chimes (Which you will always need until you have about 30) they could die and get on tilt because you didn't tell them you left.

2: If you are pushed up and need mana, roam around and collect chimes and place wards around the map.

3: Bards Shrines take 10 seconds to fully charge up.

4: You can place a maximum of 3 Health Shrines at a time, but can cast 1 on a team mate without replacing a shrine. The health shrines give a movement speed buff that decays over time. Use this to catch enemies or run from them.

5: Bards ultimate is a very useful tool, it gives vision and can save you and your whole team as well as get the entire enemy team killed and Vice Versa. Experiment with his ult, it takes time to get used to.

When playing as bard you have the ultimate element of surprise... Magical Journey! This is one of the best ways to cath the enemy off guard while returning or ganking lanes. Here is the diagram of good places to use E to gank lanes.
The red dots are where you will be entering from.
And the blue dots are where you should be exiting from.
Stuns work through walls, remember this!

If an enemy follows you through a portal, stun them when you reach he other side, easy stuns!

Bards ult is the only spell in the game that can freeze dragon and Baron Gnasher.

Meeps will slow the enemy allowing you to position for a stun and either attack or run away.

Pros:

Bard is underestimated and has extreme amounts of utility in team fights and solo battles.
Has a stun and a heal and a wall portal that allows everyone to travel through.
Has a free zhonya's that can cast on multiple people

Cons:

Since Bard is under estimated many people may not know his abilities.
His ult is a pain in the *** to land properly and can get your whole team killed.