Actually...just played Medic for one game and it's not bad at all.
Especially when you are the only one and you decide the game with an uber :V
If you ever play on 32/33 player servers it can suck if you're the only medic. Oh so necessary, but no one wants to play the class. And there are some maps where I greatly prefer to play a specific class since I can generally rape face if I have some medic support (just someone to heal me when I back off) but odds are the rest of your teammates are going to want to be selfish idiots and not pick one.
As a soldier on Badlands I can maintain movement speed faster than a scout (one place where the Gunboats are pure gold), make it to the middle before anyone else, kill the initial scout rush and usually stall/kill the rest of their faster offensive classes coming to the middle point while the rest of my team catches up. It's hard to maintain that kind of momentum if you can't get some periodic heals (or at least a dispenser), because for dealing with the third and fourth points soldiers are
fantastic because of their [potential] mobility if they have some support.
My enjoyment of the medic class is largely dependent upon my team. If you're playing with a bunch of morons then you need to realize that no matter how good of a job you're doing it's ultimately not going to make a big enough of a difference to your team's overall efforts and you're better off playing a class that can make shit dead since it will probably be more enjoyable for you as a player.
Of course, I'm a jaded player that started off playing medic back when he bought TF2 in August of '09 and has logged about 160 hours (I think a little more) into the class since then. I don't play the class very often unless I've got a few players on my friend list or some of the server regulars that I know to be competent on my team since doing so otherwise is an exercise in frustration. People with a headset usually make the game more enjoyable anyway since I find TF2 to be more boring when there's no one to talk with