Had heaps of problems here, tried the chinese drivers CH341_SER - but as the date suggested (2013) they didn't work with my very late model Mac running 10.10.4. I tried the FTDI drivers and they didn't work either. I had a look and found commercial download (cost about £5) and it worked perfectly (yes I've tested it with a tiny sketch). I'm not working for the commercial firm, and yes I bought a cheap chinese nano - but I've seen heaps of woe on this forum and it worked for me - Drivers are from Repleo and appear as /dev/cu.Repleo-CH341-00001014 on my mac.
YMMV - but I'm sure a lot of folks have given up on this and the device itself works just great - just needs some drivers specially for the mac. I guess XP, Win8 or older macs are probably just fine.