I own a Sailrite LSZ-1 and I it works great for me. The only thing is that if you want to sew any kind of lightweight fabric's it wont work very well. The gap between the feeding foot and the plate are to big and it will eat any light weight fabric. ..
We kept the older Singer and use it on the light stuff. I will add this....I was having some problem can't remember what at the moment, but Matt or Grant at Sailrite suggested that I go through the sequence of adjusting everything on the machine as if it was new (we had done a lot of projects up to this point). They have a video and I went through all of the steps and the machine is better now than even when it was new.
We can get a lot more material under the foot, yet it still sews fine with just two thicknesses, the feed is better, it is just nicer to use all the way around. I'd suggest going through these adjustments to anyone using the machine. You will also know the machine a lot better and be able to diagnose problems easier.
When we started we felt that having a machine that could go through 3-4 layers of sunbrella was all that is needed. Wrong you will at times find yourself sewing through over twice that many layers of material and sunbrella is woven so tight to make it 'kind of' waterproof that it will really push a machine. The Lsz-1 can handle that situation and after going through the maintenance procedure it does it easier than ever before. As I said before there are good deals on industrial machines out there, but I'd only buy them from someone that specializes in them and can help you down the road. If you start sewing many projects you will need that help.
The most common problem is the needle striking parts under the table top, the retaining cap or the shuttle hook with the Lsz-1. You know it when the thread starts to unravel every now and then. If you see any nicks on them you need to take them out or replace the parts. I've found that a jeweler's file and some 400-600 wet sand paper does the trick.
I also made an adapter that is simple to make for the foot control that gives you stitch by stitch control like TejasSailer mentioned. When I can link on here I'll give a link to it,