looking to upgrade my late 2007 10.6.8 MacbookPro to 10.9. Apple website says laptop is Mavericks compatible. i have virtually nothing on there to backup, just a few files that i can copy to another computer. should i just do the upgrade? what can/does go wrong?

Check that you can upgrade any crucial applications to match the new OS?
I’d do a full backup prior, then you can always revert if you have issues.

Very little, really, it might be worth doing a backup onto a flash drive of everything that’s important, but generally upgrades seem to go pretty smoothly, I’ve done regular OS updates of my old PowerBook, and since then my Mac Mini, which is hooked up to TimeMachine, and they’ve always installed fine.

As drlex says do a clone of the disk using something like Carbon Copy Cloner. You can put it back as normal if something vital that you use won’t run on the new OS. I’d recommend making a USB install disk, booting from it an nuking the HD back to the stoneage (full 3 pass reformat as a minimum). Install from the USB and then clone back preferences and apps from the back-up.
Allow about 8 hours for the 3 pass reformat and another 3 or so for install and cloning.

what’s the best way to run the backup? i’m not using Time Machine on that PB any more as it’s mostly used for internet browsing and streaming.

can’t actually download Mavericks as not available on App Store. also having problems downloading El Capitan – keeps stopping half way through. any thoughts?