In general, tools that do a lot, do not do a lot well. The hi-lift jack is one of these tools. I consider it a necessity when offroading. As mentioned, this jack will do a lot, but it will not replace specialized tools. If you need a tool that will do a lot in an emergency the hi-lift is your tool. If you have specialized jobs to do, then buy a tool that will be more effective. For example, if you need a come-along that will pull 3-4 tons buy one. If you need a tool that will winch you out of the mud, buy a winch and a snatch block.
I've used my hi-lift for a number of different things, many times in a pinch when I wished I had another tool, but I didn't. In this respect the hi-lift is analogous to a Leatherman Tool, it's great to have if you don't know what to expect or don't have the room to take everything, but if you have it a specialized tool will most likely do a better job.
Clint