So after a couple of sits in my large Mantis, I think I can give a fair, unbiased review. My background has been primarily a treestand hunter for many years, however, I had transitioned to a RC harness for safety harness several years ago, and have been slowly transitioning. First off, right out of the gate, this thing light, I mean really light. My RC harness was a Petzel Aspir, and the Mantis w/ bridge, tree tether, linesman, micro adjusters and sys hauler ES all combined weigh less than just my RC harness. Not freakin' bad. You can in fact wear this thing into the woods and forget you're wearing it. +1 in this category.
Climbing with this is alot easier than with a RC harness. This is due to the placement of the linesman connection loops. Before I was really clunky while climbing, and no matter how hard I would try I would always make noise by hitting my HSS carabiner on something. Speaking of carabiners, have I mentioned how light everything is? +1 in this category.
Coming from using HSS rope straps to these was a nice switch. I really like the spliced eyes instead of knots to make loops, this small feature is a space saver too. +1 in this category.
Hanging comfort. This is where things get a little dicey. I've been playing around for a while hanging from my RC harness, with some sits way more comfortable than others. My first couple of sits in the Mantis and my primary issue is that the strap under my legs kept riding up towards my rear end. I even received the micro adjusters with mine and pulled all the way tight, they didn't COMPLETELY cup me. Now, I think there are a couple of options here. One could be to simply wear it lower. However, after looking at the loops where the bridge attach, I think this is where the problem lies. These loops are big. If you have a really low tether height and are a leaner, this probably isn't much of an issue. But, if you are a sitter with a higher tether (mine is eye height), when you sit and put tension on everything, the bridge rides up to the top of the loops, which naturally then wants to pull the saddle up. I think I have a fix for this. I took some paracord and wrapped it tightly around each loop, pretty much forcing the bridge lower on the loops. I am 2 hours into a sit now and the "cupping" is significantly better. I feel like I have some ideas for a permanat fix moving forward, however, the fixed bridge is an issue. This category for me is a push.
Accessories. I really like the sys hauler ES. It is a very functional piece of equipment, I can put both my linesman and my tether in it while walking to stand with no issue. Additionally, it easily fits my DIY backband (Mantis recliner on order and has shipped) on one side and my phone and release on the other. I also have the SBW heater and SYS hauler on order. If these are the same quality as my current accessory, +1 in this category.
All in all, I can confidently say that there is not one area where this is deficient. So, with a potential for anywhere from -5 to 5 points on my impromptu scale, I have to rate this system a 4. Good job tethrd crew. Also, I do have an idea or 2 as permanant fixes for the cupping / belt riding up.