My views on the Pyro:
Underrated, Underpowered, versatile, OVERFUN.
For me, the Pyro shouldn't be labelled as an offensive class. He's way more of a support class than anything, IMO. A Pyro can easily stop a team rush, spy-check, defend the cart (it's very common to have RED with 5 Pyros on the final meters of a payload map), but can also go for whatever the objective is, this is why I find it very versatile.
Although, I think the Pyro is one of the hardest classes to play well with. Anyone can play any class, but not everyone can play a class well. You don't see Pyros topping scoreboards very often, do you?
Also, it's the most fun class to play with. I don't know if it's about the random "mphphphmhmphmmhph!" or whatever else, but it's just great to play as a Pyro.