The Wilder bracket allows you to use just about any bicycle seat post on your unicycle and offers the ability to adjust the tilt of the saddle to just about any angle.
Strengths
For starters the Wilder bracket allows you access to the multitude of seat posts available to the two wheeled bicycle world. It comes with a brake mount should you ever feel the need - it's there.
The biggest benefit (for me anyway) is the fact that most bike seat posts allow you to alter the tilt of the seat so I can have the front of my seat tipped way up high so my back side has a much larger and more comfortable area to sit on. Another plus from this is that, with the front of the seat up high, I can control the uni much more with my thighs. Climbing hills just got easier :)
Weaknesses
The bracket is heavy weighing almost as much as a light seat post.
Before getting one of these I was used to gripping the seat for seat out hops and jumps right at the top of the seat post. The rails completely block off this section under the seat so I've had to get used to holding the rearward section instead. This is just a personal gripe as some riders hold the rearward area already so it wouldn't be a problem for them.
Overall
Aside from the weight and having to get used to holding my seat in a different position I really like the bracket. The ability to use a seat post that can be tilted up has made riding more comfortable and increased the control over the uni. I'd like to see a version without the brake mount though as it's completely superfluous to my needs and would save a bit on the weight stakes.