Cubase 4 runs great in wine on ubuntu 8.10 (the last version I bothered with), not sure about karmic koala though. probably not worth the time tinkering with shit though.
not even trying it. 100% stability is KEY when i do music shit so even a little bit of flakiness or unexpected behaviour is not an option. also i use cubase sx 2.2, my experience is that newer cubases are somewhat unreliable and slower than usual in pirated versions because they are absolutely infested with copy protection and need a stupid usb dongle emulator running in the background
but yeah, netbooks with win7 are pure shit.
the netbook itself is great, loving this little thing. windows 7 is actually surprisingly very fast on this too, it's just that it's artificially crippled and has a really annoying user interface. windows 7 is faster on this than vista is on any core duo/whatever box i've tried it on
so basically:
windows 7, pretty fast, mostly unusable
windows vista, very slow, mostly unusable
windows xp, pretty fast, mostly usable (once you're done disabling everything in the interface that differs from win2000)
windows 2000, very fast, very usable, best windows ever (unfortunately some newer applications require xp so that's what i'm going with)