I am running Windows 7 and Ubuntu 12.4. Win 7 fixed a lot of the issues in Vista and seems to work really well for me. I am running it on older hardware so I can not use some of its features but that is no big deal. The next computer I build will be Untuntu only.
If you are buying a new puter I would get it with Win 8. There are a lot of new features in 8 that new hardware can utilize. I believe you can update from win 7 to 8 for $40 which is not the worst but will it be any better than what you have? Personally it would do me no good at this time being retired to update. When I was working I would always have a puter with the latest beta OS so I could get to know it as I would eventually have to support it at sometime in the future.
Ubuntu is a great OS that let you do most anything that Windows can do. I would highly suggest you download an image of Zorin. Run it as a live version. This will give you a chance to try it out and not take a chance of messing up your current system. It is based on Ubuntu and looks and act very much like Windows. It Free and what could be better than that.
If you like it You can install it as dual boot and not throw away your current OS in case someone else uses the puter and does not want to change. This why you will have the option of which OS you would like to run at boot up.
Do not be scared of Linux there are a lot of people here using Linux in one of it many flavors and will be here to help you though the transition.
I do have 2 licenses for Win7 that I have not used yet. When I bought Win 7 I bought the 3 copy upgrade because I planned on getting more puters but that never materialized. If anybody could use a copy please PM me. I could send you the ISO image.