I love my Leigh dovetail jig! Truth is, one day I hope to sell it, or maybe put it in a corner of the shop as a dust catcher. I really want to learn to cut them by hand. But, even though I don't run a professional shop, I do have a lot of drawers and case work to do, and I like the look of dovetails, even if they're machine cut.
When I bought this thing, I tried out several. I went to the local Woodcraft and tried out the Akeda, Keller, and the Porter-Cable. I went with the Leigh. I can't really describe it; It just felt better. Since I bought it, I've made a butt load of dovetails, and they've all come out just fine.
Don't just take my word for it though. Here are reviews from Woodshop Demos and New Woodworker. If those aren't enough, here are some "real guy" feedback comments and reviews from Rockler cusotmers.
The only down side of this jig is the price. Street price on this puppy starts at about $500.00. With options, it can run a few hundred more, but if you have a lot of dovetails to cut, this is the way to go. On the other hand, a really nice dovetail saw will set you back between $100.00 and $150.00 depending on the name brand you pick. So, pick your poison.
The manuals are about as well written as any I've ever seen, but as tool manuals go, it's sort-of big. There are several .pdf files are here for chapters... 1-3, 4-7, 8-10, 11-13, 14-17, and the Appendix. There are also a couple of "quick reference" manuals of my own devising. There is one for the through dovetails and one for the half-blind dovetails.
If you're a production shop or a serious hobbiest, you won't be able to beat this jig. For the latest information on any of their products, you can go to the Leigh website.