As mfillpot said, dual booting would be a definite plus. Especially if you're into Steam games. 2013 is going to an interesting year for Gamers and Linux. You can keep up with the progress here:

http://steamcommunity.com/app/221410

I've also heard that besides Ubuntu, Fuduntu (The distro with the really strange name - It was originally a fork of Fedora with an Ubuntu sounding name.) also has the beta in it's repos. Now, if only someone had a Steam account.

I have two Core 2 Duo laptops, and they both run full blown KDE systems without any sign of slowing down. I agree with Izzy1512, your hardware is fine. Sure, with newer hardware, you could save a few seconds here and there, but, nothing worth the price of a new machine.

It might be worth doing some research into how to optimize lubuntu. I bet fully optimized, you would notice a speed up that would make you think twice about needed a new machine.

I don't run Centos, but, from what I can remember from Fedora with Gnome 2, one needs to install the fonts in System-Settings in order for the system to see them. You can also use gconf-editor (I hope I remembered that name correctly) to change the font settings.

You need to point the configuration files to the font folders in order to use them.

If you thought Fedora was a good distro to try, but, didn't like Gnome 3, you could install Fedora with the KDE desktop. It's my 2nd favorite distro next to siduction.

Fedora does have Eclipse (yum install eclipse), as well as many other dev environments. It's not a bad choice, but as portaro said, Ubuntu and Debian have similar capabilities.

How are you attaching to the internet now? Do you have a router? If both machines are connected to the same router (wired or wireless), you should be able to access the files over the network.

I'm not familiar with Unity on Ubuntu, so I can't give you a first hand experience, but, you should be able to find desktop sharing software, or file sharing software in your Ubuntu repos.

You could also mount a partition that is on machine 1 from machine 2. You could also ssh from one machine into another, or use sshfs for mounting. If you just want to copy a file from one machine to another you can use scp.

There's no need to settle for usb sticks or google-docs, although sometimes they are the easier solution. It depends on how you want to share the files.

Welcome Izzy1512, the more the merrier. Visiting and seeing if you can answer questions is great. We need more folks helping out and sharing knowledge. It doesn't matter what your experience, if you can help great. Hopefully we'll return the favor.