I have used fiverr for fancy transitions, logo, banner, some thumbnails because I have neither the skill or software.
The guy who did my channel art was really helpful and pointed me in the direction of how to get more people coming towards my channel. It worked. I have a little following on tumblr, kind of.
Don't trust any SEO type things.
You meet some good people on there who are ready to put the work in. And it's $5! You can't really go wrong with that.
So overall I would say that it is pretty good. And there is some useful stuff there.