I've seen advantages with Solaris over Linux in my environment (1500+ servers) mainly in the compatibility with "enterprise" class products. IO multipathing software is a big one for us, as we have a large (350+ TB) SAN environment. We use Veritas Storage Foundation on Solaris extensively for volume management, IO multipathing and clustering. vxdmp on Solaris is simply rock solid in our environment. Running it on Linux has been a much larger hassle, and things like sdd or native multipathing on Linux have burned us with path failures causing systems to crash. LVM, although leaps and bounds above raw disks, is still no match for VxVM in terms of ease of use and feature set. Volume/filesystem shrinking and online relayout of disk characteristics (like turning a concant into a stripe or changing a 4 way stripe into a 6 way stripe) are so effortless with Solaris.
I know, this mostly comes out as pro-Veritas and not so much pro-Solaris, but I can't overstate the value of knowing that these products will work together so effortlessly in a very large environment. We have the luxury of plugging them together and knowing it will be stable. Veritas and Linux have just not worked together as well for us (YMMV), meaning more man hours devoted to debugging and setup and fewer focused on architecting the next solution for the problem that's just around the corner.
I love Linux, I use it on my laptops (Solaris definitely is not beating Linux is the desktop space) and used it almost exclusively on servers when I worked in smaller environments. But right now, in my environment, Solaris is giving me more stability with less tinkering for the same price.
