Obviously this archetype was Paizo's official, unofficial homage to the 2E Kit/3E PrC, the Bladesinger (a term that cant be used due to WotC copyrights). I read it and I was met with some indifference, and most of it stems from the spelldance ability itself.
Giving up the ability to enhance your weapon is huge, and a big part of the magus class. In return you get an enhancement bonus to speed (which is nice) and a rising incremental bonus that gives a very conditional +2 to AC vs movement based attacks of opportunity. I believe to justify giving up weapon enhancement it should instead be a base plus to AC, albeit at half the rate (starts at +1 dodge bonus and rises +1 at each increment). This is also more in line with the original bladesinger kit.
I may end up changing it for my games, but what do you all think, do you like the archetype as is, or do you think it needs to be tweaked?
I think it would be fine... if the spell list for the class was Wiz/Sorc instead of Magus.
As is? I think you're giving up too much.
But I like your idea about swapping the AC bonus's function.
I do not particulary like the archetype though I think the base magus works fine as a bladesinger already.