You name it! Pick an operating system for me to review!

I'm considering setting aside a partition on my drive for testing other operating systems and then reviewing them here. I would also test and compare the operating systems in a virtual machine.

I am still deciding on what parameters and format both the testing and review will take.

Here is what I would love to hear from you in comments here or in messages on my google+ or Facebook wall:

1. What operating system would you like me to review? Anything that can be installed legally for free on my laptop or anything I have a valid software license for is okay. I can review every released copy of Microsoft Windows for example (American releases). FreeDOS, virtually any Linux, ReactOS, Haiku, you name it!
2. What are make or break features for you? What can you absolutely not live without in an OS?
3. What is your comfort level? Do you like a challenge, or would you like less of a learning curve?

Let me know what you think. I'm looking forward to hearing your opinions! Let's have some fun with this! I plan to do several reviews so there are plenty of chances for your pick to get reviewed.