First off, their literature and customer service is excellent. Their products are of excellent quality and there are many happy users and owners, so from that perspective you cannot go wrong. I have owned and used an 18" Superjig. It is a very well made piece and you can get very repeatable joints BUT, and this is true with all dovetail jigs regardless of make, these jigs require very precise setup and very precise and properly repeated techniques to produce the same results each time. Don't let anyone tell you that (insert manufacturers name here) they will produce great results right out of the box. It is NOT true. With each of these jigs comes a learning curve. Each requires practice and technique to produce good results.
The downside is that as nice as this Leigh superjig is, the result is a dovetail joint that looks machine made in spite of the fact that you can vary the pin spacing and size.
If that is not an issue for you, then it is a good investment on a well made tool.
My recommendation is to put the money towards a nice dovetail saw and some well made chisels and put the time towards learning to cut them by hand. Much more rewarding.
p.s. If you decide on the Leigh, get their VRS vacuum router support. It give excellent support for the cuts and provides great dust collection.