If you have no designer in your team, it's quite useful to learn to become a bit of a designer yourself (good skill to acquire). Truth is, first impression matters, and no matter how good your algorithm or service is, if the site doesn't look attractive customers might never get to even try it.

So while some design polishing sounds like "chores" with low ROI, they can actually increase convergence rates with subtle touches (e.g. rounding corners) resulting in a great overall ROI.