Stumbling over linux-vserver two or three years ago I currently use it on an Athlon X2 running debian Gnu/Linux. Just for fun (it is a private machine, not really a "productive system") this server runs 11 vserver instances continously. I've never had to blame vserver responsible for a malfunction. Thank you!
For four years now I earn my money by being a System Administrator at the Institute for Informatics (Germany/Göttingen). Most virtual machines are running on vmware's GSX product. But linux-vserver is being evaluated and may be used for some of them in the future...