Okay I play a Paladin, I mostly PvP so he's Retribution (Holy is really not as good as used to be it outside of 5s tbh, plus it fits better with Mark who is my 2v2 partner and he is a Frost Mage) but I'm also gearing up for Protection (some random Blacksmith craftables and stuff).
I'll just say this: if you like the game to be easy in PvP don't roll one. Not to say they're a BAD CLASS but typical example is my only 2 like DECENT 2v2 setups would be with a Frost Mage or a Rogue. Compare that to a Druid, Rogue, etc, they have infinite possibilities. Me and Mark have played like Mage/Rogue, Mage/Warlock and Mage/Retadin and I have to say I've found the latter the most fun I've ever had in Arena. It requires perfect timing to get a big HoJ shatter combo off, but it's great when you get it right and beat standard gay Warrior/Druid team #45345345. Also having Seal of Justice is the best shit ever. I love idiots who don't dismount when it's judged on them.
Paladin is a fucking blast in Battlegrounds (if you're Ret). If I'm bored I'll just go into WSG, grab the berserker buff, find a nice healer and run around with my wings up 2 shotting everybody. It has some sick burst damage. It's a good frustration vent. Also you got blessings and all that crap and it's a nice support class if you play it right. Good luck fighting a healer in a 1v1 though. No healing debuff hurts.
However if you're going mainly for PvE endgame I think Paladin's quite a good choice. Everyone says Holy is boring as fuck (and I'd agree) but I've done a few random instances with my TERRIBLE Prot gear and man that's fun. From what I can tell Protadins are quite nice to have in raids too (best threat generation, good for tanking many mobs at once). As for Ret, I don't know many PvE Retadins but it IS, despite what people say, viable. One in a raid can add a few nice buffs (raid wide +3% crit, +2% damage to all in party, refresh judgements on target with Crusader Strike) and if you get your rotation right you can do reasonable DPS too. Good luck getting a raid spot as Ret though.
I haven't levelled any characters for a while, (and I don't plan to cause it is boring as fuck) however, it's a lot quicker than it used to be since they buffed experience gains in pre-TBC zones. Paladin's are a slow levelling class I might add.
imo go for it and level a Paladin, it has it's bad points but it's fun imo.