I am. The differences between the two versions is small but not insignificant. The newer PV 2012 RAW algorithm alone as well as the cleaner clarity function is reason enough to buy 4.0, IMO. And though I've not used the tone mapping and individual channel adjustments, I'm sure once I get them in the workflow I'll find them quite handy. But really for me it's all about the PV2012 and the conversion of all my DNG's. I've been told there may be color changes when doing the conversion but so far I've not been able to detect any.