I'll use it to do my job!
I am currently cramped in 4 GB, but with 8 GB I'll be able to carve my machine up this way using Virtual Box:
1 GB for Mac OS X doing e-Mail, Web Browsing, and of course iTunes!!!
4 GB for Solaris running xVM Ops Center
1 GB for Solaris guest being JumpStarted by xVM Ops Center
1 GB for Redhat guest being KickStarted by xVM Ops Center
1 GB for SuSe guest being KickStarted by xVM Ops Center
All within the same box... No need for a lab full of machines to develop and test what I need to do!
And when I'm not working, I'll use it with Logic Studio to produce music and videos -- I will not likely NEED that much memory, but it should allow my entire project and all the instrument samples and recordings to be buffered entirely within memory...which should improve response times during recording and playback. I have already come pretty close to using most of the 4 GB I have, and I'm only about 3/4ths of the way through some of my projects. So, yeah, 8 GB will give me headroom and I'm still ahead because I didn't need to buy a Mac Pro to get there.