The British equivalent of OSHA commissioned an engineering firm to do a massive evaluation of everything that gets used in "work at height". What climbers consider self-belay devices, are referred to as "rope grabs" in the factory realm.
The test included a 3 kn drop to determine if the device had an appropriate level of slippage to add some dynamic safety. They also did a catastrophic 10 kn static drop. They tested no toothed devices, as they considered them inappropriate for this application.
The three hands-down winners were the Petzl Microscender, Petzl Rescuecender, and the Troll Rocker. At the failing end of the test were the Shunt and the Ushba (At 5 kn the Ushba folded in half and cut the rope). The two Petzl units showed no sign of any damage in the 10 kn drop.
I’ve used the Microscender for over 15 years when top rope soloing. I place it at chest level with a chest harness which links to my doughnut. In hundreds of top rope falls it has never failed to grab instantly (And yes, Pete, I do use a backup, usually a toothed ascender or GriGri).
I use the mini traxion with back up knots. I can't imagine soloing without having a back up. The first thing I learned about climbing beside not stepping on the rope was to "always" backup my protection. Even when I jumar, I use either a grigri, make knots or I use the traxion for back up.
I think my life is worth a little extra work. Plus, I once had a jumar fail while I was moving up with the other jumar. Without the grigri catching me I would have had an interesting ride.
I don't want to buy more gear. Why hasn't anyone mentioned just using an ascender with neck loop? I have both the regular Petzl Ascension (typical handled bigwall ascender) and as a back up a petzl "basic" ascender. Any reason these wouldn't work? What's the purpose of the pulley feature in the mini? I don't get it.
In the past I've tried ascenders and modified Gri-Gris and have now settled on the Mini Traxion as well. I found that I wasn't 100% comfortable without a backup though, so my solution is to let the Mini Trax push a prussic along on top. This cord gets clipped in to my harness with it's own carabiner. Tying backup knots just isn't practical unless you're climbing routes with ledges or other hands free stances.