The dynamic updating. I really like that if I change a profile, my grading adjusts and so do my volume calculations. The fact that it has a memory leak and is really picky about the order in which you install the service packs is not as important to me as the philosophy behind the software. The 2006 version was quite new; a second issue, I think. I'm hoping that 2008 will be much more stable; I'd heard that 2007 is. Also, it ran really well on our dual core Athlon 64 at home, but the office machine was a circa 2006 CAD station and I was running a 300+ acre DTM.