I have 2. I have one (1/2" drive) I bought from Costco 5 or 6 years ago (12v), and while it doesn't hold the greatest charge, it still works and hits hardest on bolts. In the day and time where it's cheaper to just buy a whole new set up; I'll replace the batteries on it because it's that good.
I also have a Makita (iirc 18v) (3/8" drive) that I just got last year. I like the makita because it's light, robust, cheap (got it as part of a kit), and reliable. When I bought it, I looked at Milwaukie, and Dewalt as well - I felt they were all pretty much the same, so it came down to price. Of course, it would bear well to note that I was looking for a cordless sawzall (that was the impetus of the purchase) so the cordless impact was a nice addition, but it wasn't the reason for the purchase.