Hi daveanpat,
I'm a Linux user & find that it works fine for me. The great Windows v. Linux question has been done to death elsewhere many times before; there are members of both camps that feel passionate about their OS.
Like xrchris, I'm using Ubuntu, which has good community support & is easy to set up & get working. If you'd rather have some support backup, you might consider paying for a supported distribution. Take a look at Distrowatch
http://distrowatch.com/ for descriptions of the various distributions available. SUSE is probably not a bad choice for someone who's never used Linux before.
The bootable CD distributions won't write to your hard disk unless you specifically request to mount your hard disk or a USB drive in order to read / write to it.
Linux doesn't work with all hardware. There are Linux compatibility guides available so that you can check that your new hardware will work before you buy it. Having said this, the only compatibility problem I've had is with modems.
If you want to try Linux because you're looking for a good, stable OS that's easy to maintain & learn about, you could do worse than to give it a try. If you're looking for a free copy of Windows, Linux is going to disappoint you as there are many differences between the two systems.
Linux and it's associated software is updated regularly. The distribution that I use
http://www.ubuntu.com/ has a new release every 6 months with regular updates in the interim period as software is improved.
I think downside's experience shows us:
1. It's worth getting a recent distribution. Your transition into Linux is not going to be eased by attempting an installation from a distribution release of 3+ years longevity.
2. Linux is not Windows. Anything that is not I.E. will look slightly weird compared to I.E.
(although it is actually possible to run I.E. under Linux. )
Arnie.