(You don't need to use LaTex or any other markup language.) It is reasonably feature-rich (I gave 4 stars due to lack of iOS compatibility). If you don't need iOS compatibility, and don't mind being chained to the paid upgrade cycles, the software performs well, and the ease of use (which I gave 5 stars) is its strongest point. (TexFog is a handy free app that makes this easy). I just typeset the equation, compile a PDF, and then cut and paste. I'm now making all new slides using LaTex.
I tried manually installing all the fonts, and converting their non-truetype fonts into truetype first, and then installing these on my iPad using AnyFont.app. One thing that would make upgrading worth the additional fee would be Keynote iPad compatibility. I basically need this only for editing slides in Keynote that contain mathematical expressions. They kept all of this, including the need to pay for an incremental upgrade, well hidden at the time of purchase. The upgrade to 6.7e (as opposed to 6.9 for windows users) involves a hefty upgrade fee. What I did not appreciate at the time is that I had bought a non-universal application with no upgrade path to intel macs (which appeared 4 years previously) that depended on Rosetta (which no longer exists in 10.9, 10.8, or 10.7).
