My main is a lvl 46 fire/ice blaster who has also got the fire mastery epic power pool.
I found most of the low down ice powers a waste of time but ice patch, build up, ice sword and the one that incases the foe in a total block of ice (sorry can't remember the name) really good. But i found the last power in the pool a total waste of time, it never hits anything even though i've got it slotted with holds.
The ice block power along with char from the flame mastery pool is brilliant for holding everything from minions ro even AVs some times!
I've got nothing bad to say about the fire pool at all
Over all i have found the Fire/Ice blaster to be a great build