You can download Solaris 11 for free from Oracle. If you don't subscribe to a support contract you don't have to pay for using it (that used to be different, you had to pay for support).
As with Linux (compared to Windows), Solaris has the problem that less people are familiar with the use and administration, and therefore there will be fewer people that can help out. It depends a bit on what you want to do with the system (software development, just playing around) if that is something you should try.
Please keep in mind that some Unix/Linux software that in principle should run on Solaris, might actually only be tested on Linux, because the developers do not have access to a Solaris machine.
You can also try out a Live system for 11.1
All downloads can be found on the Oracle site