It's definitely challenging to heal in Cataclysm and that's by design. We want players to pick and choose what spells to use and when. Those in your group will also need to be conscious of whether or not they're putting out enough DPS, taking too much damage, and more. You'll probably be pulling out more "tricks" from your bag than you've been doing in awhile. You're also going to miss a time or two, run out of mana at a bad time and find yourself trying to figure out just what went wrong. Even experienced healers are going to have to dig their heels in a bit.
That said, we're keeping an eye out for how healing is going and should we feel there need to be adjustments, we'll make them. As many have noticed, we're starting to get a larger population of level 85 players who will be running through the content and getting better gear to compliment their spells and abilities. That should help some.
So far I can say as a shaman I think you really hit your mark with the pick-and-choose your spell, and I want to say it's made healing a lot of fun (and I loathed healing through WoTLK cause it just involved me keeping up Earth Shield and spamming chain heal).
I have to decide when the shock, when the unleash weapon, when to riptide, and how to stack my bonuses/group heals to get the most bang for my mana-buck. I have had way more fun healing than DPS'ing so far in dungeons.
I haven't been in heroics yet, but my guess is that the mob damage might be slightly too 'bursty'. I say this because this is the only time I've had the pick-and-choose model break down in regular dungeons. The tank gets smacked for 50% HP (while they are hovering around 50%) and it all breaks down. You have no choice but to spam your flash heal cause you can't waste any GCDs on things that aren't going to get HP rebounding fast (unleash weapon for example).
Now, if the bursty-dmg was followed by a time at which low-rolling group damage takes effect that gives the healers time to pick-and-choose, but if it's not then your group is in trouble. That's a fine line though, as I am sure you can appreciate, because you want that pressure on the healer to pick-and-choose wisely, but you can't give them too much breathing room or it falls back into the WoTLK tedium.
Besides that, there is probably a lot dps/tanks aren't doing that they should be, because they're use to not dying while pulling max dps all the time from WoTLK.
Anyway, great job with healing so far. I've actually be shying away from my DPS spec in dungeons cause healing has been so much fun so far *thumbs up*