My hardware is a Dell Latitude D830 laptop (64 bit) with 4GB RAM. I desperately wanted to run Ubuntu 64-bit as my primary OS but this is my work computer and I'm tied to Winderz (32-bit XP) for many of our in-house apps as well as my DBA tool (DB Artisan). Wine sux IMHO so I wanted as close to real Winderz as I could get.
Setup was a breeze but admittedly getting the tunneling to work was a bit tedious due much to my ignorance. I needed my Winderz vm to have a true IP Address separate from the host OS. And since I take my laptop home on the weekends / holidays I didn't want to be dinking with static IPs.
However once I had gotten this all set up it is so frick'n stable. I do shutdown the Windows VM every night just like I would if it was my primary OS but leave Ubuntu (oh how I love thee!) up all week long. But it has never crashed on me or caused any issues with my host OS. It boots the VM amazingly fast. I couldn't be happier. AND THIS IS FRICK'N FREE!
Several of my co-workers are running Macs and Parallels for their Winderz VMs and complain about the constant crashing and hanging and sluggishness. I'm trying to get some of them to try VirtualBox but most would rather complain about something they know than try something new.
Oh well, just wanted to give my $0.02 about VirtualBox and no I don't work for Sun!
Oh and for those of you afraid to take the 64-bit Linux plunge, I'm running Hardy Heron and I have absolutely NO issues with 32 bit vs 64 bit. AND I get my full 4GB RAM plus a swap file. So my Winderz VM get 1GB RAM still leaving give or take 3GB for Linux.