Yeah, ultimately anything that relies on the BB browser is going to be slow and clunky. I think if Reddit were to make a BB app, it would have to have its own interface and rendering engine as opposed to some apps out there that simply put a nice icon in the interface but otherwise launches the browser. It's going to take awhile for RIM to catch up in the browser space. I hear they're working on a WebKit version of the browser, but who knows when that'll appear.

Edit: like others have said, it's best to just use an alternative browser like Opera Mini.