The are ups and downs for each class and everyone also has a personal opinion.
Overall, we have amazing lore, at least much better than other classes. Then each spec is widely used. Many Paladin tanks in raids and instances and they are good, Retribution is finally good DPS and also many use it and holy Paladins are demanded as well. Only bad side is you need different gear for all three and even more different gear for for PvP. So if you want to do PvP and PvE with at least two specs, that is four sets of gear, with three specs it is six. personally I have Holy and Retribution for PvE and Retribution for PvP and I get annoyed keeping three sets.
I also like the spells, I think they are pretty unique and fun. The auras are imba and the 20% mount one does make a difference at least more on ground mounts.
Bad side is that you mentioned you want to play ret, there are so many ret paladins out there, it is hard to get a good spot in a raiding guild where always demanded since there are so many out there, one of the reasons why I put ret spec aside to second spec and took holy as main spec, it was more demanded. I would recommend going tank/holy and ret as second for dailies and questing. Dunno about tanking spec, but you can slap yourself from the slow kills in holy (at least compared to ret speed).
Also Paladin tends to be a more simple class to play (especially in holy), yet I still think it is important. Most of the time any other class out heals a holy paladin in raids, but with decent gear paladins deliver imba casts that others can't. Over 20k heals in one click is no problem. Also, this situation is not important, but the trash on Mimiron where you can capture a spider (you start out with low health) and spam heal him, you can do amazing HPS. A friend did over 12k and I got to 10.5k (then ran out of mana and went down to 8k), but that is ofcourse spamming an elite mob with low health, you would never be able to do that during a proper boss encounter or when I had a trinket proc, put on wings at the same time and got my crits up to 33.5k in one spell cast, pretty imba. But these are both non encounter situations, just shows that single target healing is pretty powerful and most guilds prefer a Paladin healing the MT or the OT, but when it comes to raids most of it goes to overheal or you get cut off since other class' aoe healing is quicker than yours. You also virtually never run out of mana though. Hopefully with the beacon buff in 3.2, the raid healing would be much better. Also plate and a shield (if holy) is nice time to time.
I personally love this class the most even though I did not play much of other classes (mage was main in Vanilla and TBC and in TBC tried druid and shaman for a week or two at level 70 and was not a fan of them). Try it, maybe you would like it.