I threw one against the PCs last session, and it did fairly well. Not quite as terrifying as the full-offense berserker, but good enough.
Given enough time to buff, the battle sorc can become very potent indeed.
Arcane strike feat: a must for any battlemage type
Greater heroism: +4 to attacks, saves and skill checks, +1 temp hp/level
Stoneskin
Haste
Displacement
Shield
Mage armour
Enlarge person
Maybe Tenser's, but that kills your spellcasting for the duration.
The killer is the time taken to get all that going. IMC sorcs get to use Quicken, which helps things greatly. However, getting items where possible (cloak of displacement, boots of speed, actual armour and shield) will still help things a lot. The nice thing is that you're not completely useless without the buffs; you're still a decent fighter and you can also resort to boom spells in a pinch if necessary.