It is the only one which provides support for so many popular computers! I don't know any other PC AT emulator... However I have a question about the exactness of the emulation. I run several benchmarks and the results are problematic. They show that PC 5150 and PC 5170 emulation is significantly faster than it should be. 
For example, with https://dosbenchmark.wordpress.com/ for PC 5150 I got that PCem is 25% faster, for PC 5170 PCem is 64% faster. The older tests give the similar results. I am seeking a way to test the speed of the real iron. I have a project at http://litwr2.atspace.eu/pi/pi-spigot-benchmark.html
So I am seeking the opportunity to get the results for the π-test. Any help? Please.
I use PCem under Linux. I missed the several features. IMHO the "full throttle" or "warp mode" button will be very useful. It is a bit unexpected that PC 5170 with CGA card starts at 40 columns mode - PC 5150 starts with the normal 80 columns.
BTW I like to write programs for the retro hardware, my latest PC project - http://litwr2.atspace.eu/xlife/retro/xlife4ibmpc.html
