I've actually really been enjoying leveling a Holy Paladin through older content, although it is remarkably easy with heirlooms. The real test of my enjoyment of the spec will be current content. It's a little weird not having to deal with Holy Power anymore, I liked the throttle on mana usage you used to have but I like the lower level healing talents the spec has now. With Bestow Faith and Holy Shock you can be pretty mobile healer, I used to struggle with any healer outside of Resto Shaman and old Disc Priest keeping up with some tanks. That isn't the case with Holy Paladin anymore, even if your movement speed bursts are somewhat sporadic versus spirit wolf or shield boost.
Even though the mastery doesn't come into play until 78, Consecration (and some later talent options) sort of encourages you to be closer to the melee scrum so Holy Paladin does feel more like a battle healer, like some melee equivalent of a Discipline Priest in a weird way.
You definitely encounter more weirdness as a healer than as a tank in PUGs, or at least that's been my experience. There's always some people doing goofy shit, queuing as tanks but playing DPS, people with nutty heirlooms for different classes, all of the weird fighting people get into.
