I am getting ready to install OS X. I see that it gives me the option of formating my drive/partition to either Unix or Mac OS Extended. Does it matter which one I use? Do all of you suggest one over the other?
It really comes down to a choice of using Mac OS X with a focus on the Mac side or the Unix side of things.
HFS+ is the choice for Mac users. A lot of meta-information about each file is preserved. File name capitalization is preserved, but the system doesn't see a difference if you want to use "My Report" or "my report" which is what most Mac users expect. It's also the more compatible format if you're going to be going back and forth between Mac OS 9 or you want to have better compatability for the Classic environment.
UFS has it's good side, but overall it's the type of file system that meets a Unix user's expectations. It is fully filename case sensititive. It preserves virtually no extra metainformation about a file. It isn't viewable by Mac OS 9 and may give some Classic apps problems.
If you come squarely from one camp and want to "test the waters" in the other, I'd suggest making the boot partition be HFS+ and have another partition that's UFS.
Most Mac users will probably stick fully with HFS+
I have two hard drives in my B&W 300, so I installed OS X on the second drive (much easier then partitioning). The first time I installed I used the Unix format everything worked except the Classic environment. After installing a clean copy of Mac OS 9.0.4 on the first drive I still couldn't get the Classic to work. Last resort reloaded OS X using the HFS+ format, results Classic works.
Thus my suggestion: if you want to use the Classic environment, use the HFS+ format.