ac servo motors

Hi all.

I have to build a precise positioning device.

I am experineced with stepper, but now going for servos.

Having actually decided for dc brush, i have although guessed about ac
induction.

There is a plenty of rumors about using them for cnc, and in my case
another major reason is great availability of small power commodity
units at a good price.

But what about drives? There are a lot of inverter ac speed
controllers, but for positioning...

I have just got a glance at Advanced Motion Controls drives, but I
don't know if I understood well.

Are these drives capable of position control of an ac induction motor?

Has anyone experience of such devices?