I find healadins to be incredibly enjoyable, but it fits my playstyle, especially with the PvP set that complements it nicely.
I spend my fights actively seeking out ways to gain Holy Power, and the set bonus rewards me each time I do. It's like magical unicorn-made cookies! I get two, and bam! Instant, extremely powerful heal with bonus shield and HoT. As Amabella mentions, the Beacon glyph totally rocks. A no-mana Beacon swap off the Global Cooldown? Yes, please. In the space of 3 seconds, I can toss it out on anyone that takes damage, hit them with Divine Light, throw in an instant spell like Holy Shock or EF while I wait for the cooldown on Beacon to finish, then shimmy it back onto the tank.
Boundless Conviction and Holy Power banking adds a new dimension to our healing repertoire. Instead of HP being a boring resource that we expend like clockwork when we hit 3 points so as not to waste any gains, now, you basically get to have a permanent pocket heal with the option to store up healing energy for about 10-20 seconds in order to meet an upcoming massive blow attack head-on.
Playing a paladin is a lot like constantly saying, "Oh no you didn't!"
Tank health dropped too low? Lay on Hands.
Cat jumped on your keyboard? ...Lay on hands.
Raider needing a quick heal? Instant-cast Word of Glory/Eternal Flame.
Boss about to use a heavy attack? Hand of Sacrifice.
Teammate got aggro accidentally? Hand of Protection.
Melee teammate pulling mobs? Hand of Protection, and that'll teach him!
Can't get out of the way of a doom attack? Bubble.
Don't feel like getting out of the way of a doom attack? Bubble.
Stuns, snares, slows, DoTs, death circles, deaths... if it can happen, we have an instant-cast answer for it.
Edited by Wards on 12/24/2012 7:10 PM PST