Mushkin itself is one of the few top of the line RAM manufacturers on the market. I don't have experience with them in macs, but their general track record makes them a top performer in all conditions.
I just bought and received that EXACT item from NewEgg, as it is a great price after rebate. I had not heard of Mushkin before either, but some coworkers of mine had and similarly said that it is supposed to be quality RAM. It's working just fine for me...that's all I can say, heh.