"Before, you had to be a big Sun customer and sign a lot of [nondisclosure agreements] to beta-test Solaris. For Joe Admin, that just was not attainable," said Dale Ghent, a systems administrator at the University of Maryland at Baltimore. Ghent is in the process of moving 30 servers off of Red Hat Enterprise Linux to Solaris. "Being able to test Solaris Express early gave us a psychological level of assurance," he said.

Some users are even embracing Solaris Express for production. Last year, San Anselmo, Calif.-based Web hosting provider, Joyent Inc. moved hundreds of servers and nearly 100TB of data onto Solaris Express and off of FreeBSD and SUSE Linux. Hoffman said the move has boosted his data center's performance while cutting down on costs and crashes.

"Once you've watched a bunch of your commercially-supported Linux servers crash every third day, you stop worrying that you can't officially call Sun for support," Hoffman said. "Some of our servers haven't been rebooted since we installed Solaris Express on them many months ago. They just sit there and make money."

Hoffman cited cutting-edge features available first in Solaris Express, which is updated monthly, for his willingness to experiment. They include ZFS, a 128-bit file system that can store radically more data than conventional 64-bit file systems; DTrace, a bug-finding tool that can be used even while servers remain online; and Zones, a virtualization technology.

Open-sourcing Solaris has also helped Sun rebuild mind share in an area it long ceded to Linux: on campus. "Until Solaris became open, students were only interested in Solaris for the same reason they were interested in NextStep Unix -- because it was this arcane, old-fashioned thing," said Asheesh Laroia, a graduate student in computer science at Johns Hopkins University. "There's been a major upsurge in interest in Solaris. So many people are asking, 'Should I install it?'"