Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Good lord. I couldn't watch more than the first few minutes. For a Mac youtuber, you'd think he'd do some research before making a video. The version of InterWeb he used was the old one (which is based on 52.9 not tenfourfox like he says) rather than Jazzzny's newer build. He didn't even bother or know to try Pale Moon, Basilisk or SeaLion either. Also, does he not believe in ad blockers, hosts files or script blockers? I have old powerpc's that run the web faster than that. Trying to load YT with no ad block is just stupid. The first 15 minutes of that video made that machine look 10x worse than it is. I know because i have one, and it doesn't suck that bad. That's about where i quit watching. He's done some great videos in the past, but this isn't one of them.
 
My answer to that question is yes, yes it is useful. With SSD/RAM upgrades and up-to-date browsers like those mentioned by wicnix (especially Pale Moon/ArcticFox and InterWeb), a machine like that is still fully capable of everyday web tasks for someone who just needs a computer for getting around the Internet.

To really maximize its utility, there's also Linux, which affords access to a lot more up to date software, too. A lot of people to harp on the 2006/2007-era Intel Macs, but they're machines that can still punch above their weight with the right software.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.