I raid 10 mans. I enjoy healing on my Shaman. I don't feel weak.
However, there are a few things that bug me. Blizz nerfed our Mana Tide, but attempted to balance the nerf with a mana-per-crit mechanic. Which in general is OK, but it has some significant issues. First, this mechanic is tied to Water Shield. In the same patch, Blizz made just about anything proc water shield. Which is bad, because when the shield is down, we get no passive regen and no crit regen (and the mana we get for a proc is tiny, too). The fire birds before Alyxrazor is a good example of this: my water shield disappears in literally 2 or 3 seconds, for no discernible reason. Second, we get no mana return for casting Healing Rain -- which costs a ton of mana to maintain, and is absolutely mandatory on the AoE damage phases of bosses like Majordomo and Ragnaros.
Honestly, the biggest issue I have with my shaman is that I don't feel like I have a lot of control over my mana. On my Druid, in considerably less gear, I can spam quite a lot before getting into mana issues. Granted, solo tank healing feels way, way better on my Shaman, but for everything else, I'd rather use my Druid (too bad my guild has a glut of good resto druids).
As an aside: while Spirit Link totem has some amazing situational uses (e.g. Ragnaros p2), it's not that great of a reactionary tank cooldown. It has a 10 yard range (and is dropped randomly somewhere 2-3 yards near you), so you need to be almost on top of your tank to use it. Even then, it only reduces incoming damage by 10% (plus the health balancing every second or so, of course). This is great if you know the damage is coming, but if you don't (e.g. a tank is randomly spiked too low), it's worthless. Which is why I somewhat object to calling it a "tank" cooldown.