Functional improvements with user feedback have paid off. However, the overall graphic design is still where it started -- it's not easy to replace L&F.
Graphic design can make all the difference, but we'd like to ask HN: Is this sort of expensive rework worthwhile, when functional tweaks are available for A/B testing?
I think the basic layout is there, but you need more of a lightness of touch, that you would mainly get from someone who does CSS polishing all the time.
The graphic design is quite good as it is, but a graphic facelift is not that expensive, so long as you stick to re-skinning the site -- CSS, images, etc. -- as opposed to major layout and content changes.
So, yes, go ahead with that. It's at least worth trying.
I'd say that FiveYearItch exists to get people job offers. So, the graphic design is not core, and you don't need to sweat it.
For sites like yours, you want users to sign up, not to spend all day on site. Stickiness is important, but your priority has to be customer acquisition, and for that, the design is fine.
No need for any changes.
I registered at FiveYearItch a while ago, and it is doing quite well for me. So, keep it up!
In that case, stick to what you are good at and polish functionality.
Some top webapps have done well with weak design -- take a look at Google and FB.
(just signed up, but defintiely you could be a lot "cleaner")