I had lots of problems with the USB version (that I could work around though), however recent updates to my Imac and IRTrans fixed these.
Personally I would take the Ethernet version if I had to choose right now, it seems that sometimes my USB version falls asleep and it takes a few seconds before it wakes up and reacts. I can't find out a logic around that though but I am guessing the USB port powers down after a while of inactivity.
There was a simliar thread on the german forum some time back and another person recommended the Ethernet version as well, for similiar reasons.
Otherwise it is a brilliant piece of software, I can certainly help you with the setup of the software if you want to control Frontrow.
Cheers
JK
BS9000, BS2300, BC2, BL2500, BL3, Bl2, BS1, BV8, BC4, A8