I have a Mint LP (SOTA/FR64fx), SMARTractor, GeoDisc, and Graham alignment jig (Phantom Supreme). Really, if you have (or can make) a good visual marker for the center-of-pivot on your tonearm, and are confident in your line-of-sight accuracy, the GeoDisc has a really nice combination of: universal, reasonably accurate, extremely easy/fast, and very affordable. The simplicity is beautiful. I still use mine for a quick and dirty install; less hassle than any other method.
The MintLP has the best alignment scheme - more than any other mirrored protractor, its markings are well thought-out to make incredibly clear whether you’re dead-on perfect or just off. It even works well for cantilever alignment with big boxy bodies like Koetsu and Shelter (usually very hard to align cantilever because it’s largely occluded by the body). It can also be made for a Graham Phantom. The big flaw here is: you need one per table/arm setup, and the spindle-to-pivot distance it was printed for MUST be matched by what’s on your table. Even when you specify a P-2-S distance for a custom arm-board, the end result can easily vary by 1 mm or more. So all that precision alignment might be for naught.
The SMARTractor is definitely a cool toy, but I don’t have as much confidence visually aligning to its markings as I do with the MintLP. I hate that little "dot". It’s also very hard to align cantilevers on a boxy Koetsu/Shelter, because the alignment pipes are too damn far back. I sometimes resort to aligning by body, which is not ideal and defeats the point of a $600 protractor. The P-2-S measure feature is sweet, but it won’t help with a Graham Phantom where the center cannot be precisely discerned from top (I stick to the Graham alignment jig/tools on this arm). However the SMARTractor works brilliantly with a ClearAudio Universal, which has a little top center divot for the SMARTractor’s arm spike to fit/lock into.
The Dr. Feikert looks like a very nice package/price.