I have, by far, used my hi-lift more for winching than for jacking, but it's done it's share of lifting jeeps over the years as well as buildings, trailers, trees, and other really heavy stuff.
Like others have said, you have to determine for yourself whether it's going to be easier to use the stock jack, or the hi-lift on a case by case basis.
Heh, on my old YJ, which I never had lockers or a winch, I used to use the stock jack to get unstuck. Let me tell you what, you become a pretty good wheeler after a while of getting stuck, and having to use the stock jack to get you out. Upgrading to the hi-lift, a ten foot piece of chain with chain hooks on each end, some strap, and clevis was a big help. I was then able to hand winch the Jeep out, though it was laborious. A lot of people jump straight to an electric winch these days, which is almost cheating! :cheesy: I blame it on ADD. Can't take the time to learn how it's much more important to not get stuck. :laugh:
I upgraded the handle to a piece of rigid EMT, because it makes a better sleeve for ruined tie rods, and it's not a bad hammer now either. Good for prying as well.
I have used the jack to lift sheds, garages, and other small buildings, in addition to vehicles and trailers.
I knew I had this old page bookmarked somewhere, it's a quick rundown of how to use it for other things:
http://www.4x4now.com/bb0997.htm
Here is another one, a bit more updated:
http://www.offroadadventures.com/articles/view/id/347
In any case, now you know there is a lot of uses for the jack, besides changing tires.
Respect the Jack, it's a tool, and it can screw stuff up as easily as repair. If used incorrectly, or in an unsafe manner, it's easy to get hurt. I have been pinched, punched, whacked and had a Jeep fall off once. I have heard of people getting hit in the face with the jack handle too. Luckily never experienced that one. I pull the handle when I am done jacking the vehicle UP.