I don't know much about the Ultramag, but I do know that Hoyt makes a great product, and you wouldn't be dissappointed with the quality.
If you can, find a pro shop that has one in stock, and try it out. Only you will be able to determine if it's the right bow for you. If you don't like the way it shoots or feels, then you've wasted your money.
Good luck, and let us know how you make out.
No bashing.......Violators will be shot.......Survivors will be prosecuted.