During the Lich King era mana regeneration became more and more a non issue for healers. And even since the 4.0 patch heal spam and overhealing still reign supreme in raids. The healer metagem of choice still sticks to Insightful Earthsiege Diamond though, I would dare to say more by habit and having used it for now two years.
An interesting point to not though is that there is no upgrade to this meta gem in Cataclysm. The insightful gem disappears from the scope entirely. There is a reason for that, and it is very simple. With the increase of healing spell cost from 80 to 85 and the amount of raid damage of most Cataclysm raid fights, an upgraded Insightful gem would be very very overpowered compared to the other meta for healers.
We do not have final studies at lvl 85 for metagems, because the value of each stat (int/crit/haste/...) has not yet been set for every healer class. But some people have already given it a first look and it seems even at lvl 85 the old Insightful Earthsiege Diamond could still be the best healer metagem. I find it a little silly to use an outdated metagem and usually blizzard corrects the values when something like that happens. But ask to shield using tanks, they would tell you they used a BC enchant for their shield during all the LK period.
So don't sell/drop your Insight yet, you could still use them in Cataclysm.