I hunt exclusively out of ladder stands, 80% of them are of the homemade (wood 2x4) variety, most of them are in the 15" range.

If you are going to buy a metal one, make sure the seat flips up, makes a world of difference in comfort and having the ability to set up for a good shot.

The most important thing about a ladder stand is tree selection.

A single trunk tree with limited branch cover is setting yourself up for a lot of frustration. (excluding a good bushy pine) If at all possible find a double trunk tree and wedge the stand up into it providing you with a nice back drop that will allow you to blend into the skyline.

The difference between a 15' stand and a 20' stand is huge, that extra 5' is usually enough that the deer will make it to and past the stand with out them busting you if you do make some movement. (of course you have to play the wind properly but that holds true for all stand placement)

And whatever you do, don't forget to use a saftey harness, even with the rails on the side of a ladder stand, it is an illusion of saftey.