There is an 8th-level Genasi (Firesoul/Windsoul) Swordmage in my game. He took the Aegis of Shielding, though he hasn't neglected Strength. He's kind of a hybrid between the two main builds.
He doesn't control the battlefield as well as a fighter does, but his shielding abilities mean he might as well. Seriously, a foe marked by him basically can't do any damage to anybody else. And he, himself, has the highest AC in the party, by several points, at 27 (14 + 5 Int + 3 hide + 2 enhancement + 3 Aegis). If they attack someone else, they do 8 less damage in addition to the -2 to-hit.
So, basically, a single enemy is rendered completely useless except against the Swordmage. He did a real number on an Ettin last session.
As for offense... well, he's not great. He has both Greenflame Blade for short-range and Lightning Lure for somewhat-long-range. He picked up Bastard Sword, which helps, but the most damaging attack he has is an immediate reaction upon being hit - which doesn't always happen. Otherwise, he's looking at 2[w] max with few ranged attacks.
OTOH, he can move all around the field almost at will. His Utility powers are generally teleport-related, and he has Serpentskin Hide to really twist the knife.
My player really enjoys running him. It's a very weird class - lower on offense than you'd expect, but almost insanely good on defense. Very much a defender/controller. He can clear out minions, or lock down solos & elites, but is ironically weakest against normal enemies.
A few notes that are easy to overlook:
(1) Don't get knocked unconscious. This will nuke your AC bonus.
(2) The damage reduction aegis is an immediate action. Keep in mind you can only do it 1/turn.
(3) Try and mark an enemy, then get the heck away from them. You have almost no reason to actually attack the guy you marked. On the DM side of the screen, it's kinda irritating.
-O