I haven't ever had too much trouble with this software when it comes to it running quickly and efficiently. I'm always able to run as many MIDI tracks at once as I need to and it always runs smoothly while doing so. While it depends what system you are running it on, as I've only run it on a PC, it should run pretty well even on systems that aren't all that great.
I've been using MOTU FreeStyle for about seven or eight years since I got acquainted with it during school. It is a really easy piece of software to use and because of this it isn't capable of all that much beyond its basic function. This software is designed for beginners and if you are a professional I would recommend looking into MOTU Digital Performer as it is a much more detailed piece of software. MOTU FreeStyle is really cheap and I would definitely recommend picking it up if you are new with MIDI and want to get your feet wet, but if you are serious about making music I would look elsewhere to software that is more in depth.