I play all the healing classes, Druid is by far my favorite. Perhaps because of its small toolbox in comparison with HPally and Priests (although this is not a solid argument as others may argue saying Druids at least use their entire toolbox). But that is an excellent segue into another reason, is that Druids use all their abilities, I don't think there is ever a fight where I don't use each move.
I find our toolbox to be incredibly good and competative. I do say, and perhaps this is my narrow-skill level, that at the start of 4.3 I was very heart broken at our adjustments (I refuse to use the term term nerf here), but I adapted and still battle with my HPally buddy over being a highly proficient healer.
Sure, we rejuv spam a lot more than what we used to in the start of cata and it can seem a bit arbitrary in situations with Holy Radiance's instant heals, but it's still great. Nourish is incredibly effective with our Mastery (I wouldn't complain if we got a buff for it). Regrowth has seemed to gone away for me as I don't spec for living seed anymore, but I often pop tree of life, tranq, then innervate, (with 4p t13) I spam regrowth on everyone.
Overall, I find the druid resto spec still effective, powerful, and a lot of fun. My current progress on him is Deathwing down, and Heroic Crotchrocket downed. I maintain top or second heals against my Pally partner, all very dependent on the fight. Although, I must say we are 10m, so 25m is a very different story I am sure.
As far as the other guys. Shamans are boring for me. They're very good and riptide is amazing along with healing rain. Chain heal is tons of fun, but the tool box seems a bit small, although I do feel a bit of prestige in healing when I drop a clutch Spirit Link Totem.
Priests, both specs are also boring for me. Disc can get a bit static for me as well as Holy. Holy is fun because switching your Chakra is pretty cool and very useful.
Pallys have to be my second favorite. I still feel very mobile on my pally and our abilities are great, namely the clutch cooldowns. Are they over powered? They certainly have an edge, but I wouldn't say nerf them.
So for me, I like druid because our toolbox is tiptop and effective. Barkskin is amazing. I love being mobile and able to help out positional DPS during certain fights.