I have a JLG T-350 towable manlift that is more than just useful. I rented several brands from rental companies until I found mine for sale on Craigslist. Here's my experience: (I'm 1/2 blind right now from being at the eye doctor, so bear with me):
1) You will need to get used to going up more that just a few feet. Some can't do it. There can be a little shakng going on until you learn to work in the basket. Don't try to prevent the shaking, just lean on the cage and ride it out. When I am at 32' (platform base height), you can't move laterally a lot because all the arms are straight up.
2) Mine is self leveling. You move the lever, It adjustd the legs until the turret is level in all directions. I tow it with my tractor to multiple locations, even with the stabilizers just a few inches off the ground to the next location.
3) Painting a barn side, checking gutters, trimming trees, and servicing my windmills is a breeze.
4) Mine is battery powered. Some are gas engine powered. The quiet battery operation allows you to talk to ground helpers without shouting and the usual yelling.
5) my basket is removable and can then be fitted with a jib crane (Which I made myself). I hoisted a very large cupola up onto the garage roof and put it in place in a minute. Would never have made it without the lift.
6) a very heavy rig will most likely sink into the ground under it's own weight. If the ground is soft (as in moist soil, under roof eaves or sand), it may be hard to pull out or could tip). Mine, BTW, uses the auto level features to watch for any sinking or overloading or over-reaching). It will stop the movement with a flashing warning light if this happens.
7) My electric one's battery charge lasts for days, so no need to worry about getting stuck.
8) Towable also means borrowable. No need for special trailer pulling capability or other transport issues.
9) A lot of fun stringing Christmas lights, fixing weathervanes, cleaning out the martin houses, changing out the flag pole rope (the one that jumps the pulley 25' up) and examining the local deer population when the time comes.
10) There are two types: crane and boom lift. Crane type is just a swing crane with an extension. It might take you a few tries to get the ground position set before you can arrive at the work site. Mine is a scissors type, you go pretty much straight up and then extend out to the work area.
11) I'd recommend starting out with the trailer to see if you can tolerate the height issues. If you fall more that 20' you're probably toast anyways, but some people loose their shorts when fear of flying kicks in. The more you use it, though the, better the feeling gets, especially if you focus on the job and not the height. BTW: NEVER LOOK UP. If you see a cloud moving, you are toast.
12) Download the manual from the manufacturere's website to see the arcs of travel ranges for a positioning guide. I actually bought a plastic model of mine from a ebay seller to study the ground placement issue. (I hate to look stupid in front of my friends and enemies.)
This is my opinion and I'm stickin' to it.
