I have the loops, the Tarantula 1 and 2, and even the damn Pen (almost embarrassing to say out loud lol). The loops are great. I would like to get something better to carry them in and they do seem to get fairly stretched out after a good night's use, but overall, they are pretty damn cool.
I am not a fan of the new Pen Pro because mine never seemed to work quite right and when it did, it just didn't feel right for me. Perhaps a personal preference type of thing, not sure. Also, way overpriced in my opinion.
Tarantula 1 was really cool, and the new one fixed literally every complaint I had about the first one. I am starting to make myself use and practice the T2 because it really is a great device. I have extra spools so if I am working and have a break I can just switch spools then worry about reattaching wax to the broken one when I have time (which is usually not too hard to do by the way). I also generally will have a loop on my arm when using the tarantula just in case of an emergency.
Practicing a lot with any of these systems is key. You will get to know your own style, your own device, the thread, and the amount of weight and intensity each can take as you use them more. Then you will find less and less breakage of the thread I assure you.
Last, lighting can definitely be a problem... but there is a reason this stuff is called invisible thread. I mean I have done stuff in broad day light in front of people just a foot or two away and they can't see the thread. And when I try to repair a spool or thread that just snapped, I often am astonished at just how invisible the thread is.
Hope that helped. Any other questions hit me up any time.
Best wishes to all and have a great weekend!
Matthew