I never thought about this! It could be useful for Mage - heck, it might even help balance destruction a bit! Encircle yourself in a wall of ice and prepare yourself for when the wall disappears, that sort of thing.
Or just blast through it as soon as your magic spell was ready to cast...
To be honest I was hoping for a sphere like barrier that I could create to protect me from dragon fire for a period of time... but I have to admit the improvements on magic from Oblivion are enormous! I was so thrilled but I can still understand the desire for more, more, more... thats cos we love magic and we love what Bethesda do with it... perhaps in future they will expand magic into new areas with additional spells that create this wall of ice... Hell, Id just be boxing in villagers for laughs!