For experienced users or users with access to Linux experts, xVM is already ready for prime time. Sun XVM does everything one expects from a virtualization software package, and does it very well indeed. A big plus for xVM is not having to set up SAMBA. It isn't bad on host CPU loading either; with XP and Kubuntu guests open without major running applications, they draw about 21 percent of memory and about 10 percent CPU load. With applications, it will peg a CPU meter running native, and do the same on the host OS. In other words, it depends on your application mix; there is some overhead caused by virtualization (typically 10–20 percent) I prefer to use host applications wherever possible for that reason. A user transitioning from Windows can work with her favorite applications and switch to Linux apps as she finds them and figures out how they work. It also handles multimedia better; it won't grab host audio resources until and unless it actually needs them but will grab them when it does, unlike VMware Server, which is hit-or-miss with respect to sound.
It’s just as well, because with VMware's determination to force its user base onto a Web-based platform despite loud user objections, those of us who don't want our workflow subject to browser crashes need a replacement while there's still time to do an orderly transition. So Sun xVM came along at a good time for me.
That said, xVM still has a few rough edges. I'm mildly annoyed that for Windows, I can't use 98SE and I had to get XP to make it work on USB. Note that all I keep a Windows guest VM for (as I do on VMware Server) is to run a few legacy programs (unfortunately, including my Eudora mail client whose Linux version isn't ready for prime time yet) that work just fine in 98SE. The instability and insecurity of 98SE are non-issues running on a VM behind a Linux firewall.
Sun's having Kubuntu come up during install at what looked like 1600×1200 (my entire display with the bottom slid under the KDE taskbar was a PITA). As you can see, xVM still requires command-line use to set up correctly, and this is equally true of VMware Server.
Settings for each VM guest are inaccessible with the guest running, unlike VMware Server, though the most necessary settings, individual mounting of C/DVDs, and USB devices are always available.