I suppose it makes sense that your design suggests to people if they should invest time in your idea because you invested time into it.
Seeing it in writing helps drive the point home.
Also, big congrats to the Grove team, the site and product really do look beautiful.
Thomas and I chat about this periodically. For about $15, an hour of browsing ThemeForest, and half a morning with 960.gs and Compass/Sass/whathaveyou, you can make any throwaway app look like it had someone with actual design talent touch it.
http://themeforest.net/item/simplpan-admin-panel-template/fu...
That's one I just happened to grab out of a search for "admin". Does it look like something that got Jediguruninja handling from a team of bespoke design consultants? No, but it sure craters the approach to that bridge, for three to four orders of magnitude cheaper.
You can never expect a kickass programmer to also have the best design chops. They require different forms of thinking. So stop giving false advise to programmers on enlisting design skills and instead partner with the best designers!
For $15, you probably won't get the most absolutely-custom-tailor-made experience - but you might at least get something that convinces visitors to take a closer look.
If you're a programer and not a designer, just think of your design as another optimization point.
Whenever I worry about the design/branding of my current startup, I visit the historical timeline of amazon's logo as a reminder that we'll be able to make it better eventually, but there's more important things to work on now: http://www.kokogiak.com/gedankengang/2004/07/amazoncom-logo-...
On the other hand, communications design—what you call "pretty colors and interface"—is an entirely different set of skills, honed mainly by years of critical exposure to different visual aesthetics and artisanal practice in replicating those aesthetics to understand their composition. It's an orthogonal skill to programming—but, once it has been done and a suitable aesthetic created for a piece, it's pretty easy for a programmer to take the results (a "theme"), break it down structurally into re-usable components, and then apply those components to solve their problems. The bit the programmer is untrained at, the understanding of what works with what, has already been performed by the designer.
Ive ran across apps that simply look good but terrible user experience. User experience is what separates the amateur apps to the full blown mega millions..
As a programming single-founder, you have already taken the first major step! You realize your core competency and your weakness and the importance of filling that gap. I wouldn't be that disappointed because I know of a lot of programmers that don't even take that first step. Most of them don't value design because its a foreign world to them.
The biggest recommendation I would have for you is to find a designer that will take your framework and elevate it to the user experience that makes sense to the world...
The Groove team definitely nailed it when they said that design is an important element...