There are only a few features that require SSL, and those features require it due to Facebook restrictions. Mainly, the Page Tab integration, for showing your site inside Facebook has to have SSL because when you're browsing on Facebook.com, that defaults to being in https mode. The same goes for Canvas Integration, where your site is shown in it's own larger window area within Facebook.
The Requests (invite) feature from Facebook requires the Canvas to work, and therefore also requires SSL.
There's no way to get around the Page Tab or Canvas requirement for SSL. We are looking into a way to get around the SSL requirement for Requests as we think we may be able to get those to redirect to your page without going through the Canvas first though. We aren't sure of that yet though and don't know when an update would be available to support that.
I hope that helps explain what requires SSL. If there was some other feature you thought needed it, or you needed one of the above features, let us know. We can explain more, but not much we can do for the items listed above.
When you run Autotune, it will setup your app automatically for you. Autotune will configure your Secure Page Tab URL and Secure Canvas URL as if you have SSL, but it shouldn't cause any issues with those settings configured.
All other features should work just fine without SSL. Can you tell me if you're having problems with specific features, and if so, what?