I can't speak to the employment side of things, but the work side of things is disappointing. Their recommended gigs are scattershot and a lot of the ones they push ("in conjunction with gun.io" or similar verbiage--sounds like premium postings) are six-month, monopolize-all-your-time contracts at a low hourly rate. And they don't seem to respect their own site's rules, at least not the spirit of them: every once in a while I'm spammed with a '$1,000' offer from gun.io themselves that's really "we'll pay $100 for a blog post".
Unfortunately I'm not sure that anybody else is much better! I still get most of my work through interpersonal connections and the occasional email from Hacker News readers.
I tried to register for Gun.io and the first thing they want me to do is to write proposal to see if I could communicate, for skillsets that I don't have in a field that I have no knowledge of (GRE over IPSec). I make another try and now it's to write proposal for framework that I never used with explicit "no 'willing to learn' proposals" in the body text. Maybe I'm just unlucky, but if they're asking me to BS on the proposal just to see if I could communicate, then I have to say this is definitely not a good first impression.
Good luck getting paid on gun.io, if the buyer just decides they want the work for free then they can take it and wander off. Gun.io doesn't care because who is bringing them money?
