The biggest issue I see is price. ~$100 for the base app and ~$60 for US map.
The only people I see being interested in this product would be either those who have a PowerPC-based Mac (and OS X 10.4 or 10.5) or those who have an Intel-based Mac, have not yet invested in a PC virtualization app (either Parallels or VMWare), and are NOT interested in doing so.
A query to the developer regarding pricing versus a PC virtualization solution (on Intel-based Macs) was met with a crabby response.
A demo is available but it is very crippled - only two maps are available (Yosemite Valley and Santa Fe, NM) and an obnoxiously HUGE "DEMO" watermark persists as you navigate around.
Final answer: If you have an Intel-based Mac and are amenable to using Windows, then your best solution would be to get a PC virtualization app and a copy of Windows (for minimum fuss, Windows XP is best - but supplies are drying up fast) then pick and choose which PC mapping solution meets your needs.