I started with a dual-boot Windows 7 / Mint 14 laptop, and upgraded this way to Mint 15. It worked perfectly.
When 17 came out, then I went thru the process again (was still on 15 as a dual-boot with Windows). Everything appeared to work with the install of 17, but GRUB got messed up and my laptop would not boot at all. Since I really didn't need/use my Windows 7 system anymore, I just reinstalled 17 and told it to take the entire drive. That worked fine, and I don't regret killing Windows either.

In both cases, the Backup/Restore utility worked well, and all the apps I had installed (like kMyMoney, NetBeans etc) were restored with my settings and data. I did not have to reinstall these apps, which was awesome. I believe that I DID have to re-setup my VPN connections in Networking, can't remember if it saved my actual router/printer connections, but those are easy.
I have to say that Mint 17 feels a lot more stable than Mint 15 on my laptop; my SD card reader started working, USB drives consistently appear on the desktop (in 15 it was hit and miss whether the icon would appear). I am happy with 17.