Just a couple of comments. First, unfortunately there is no Linux-specific customization yet, the reason being that I don't have enough room to install an Ubuntu VM on my laptop. I don't like this state of affairs, and would be delighted if someone would contribute proper Linux support. I am not sure Evince has support for inverse search, but I think Okular does (or used to). It's been a while...
Second, regarding the previewer in OSX (and other platforms, too, for that matter): my medium-term goal is to make such things user-configurable. Preview does not support forward/inverse search, and for me this is a non-starter; however, that's a matter of taste.
However, I am about to merge patches that implement better interaction with the PDF viewer and, more importantly, proper error handling. This redefines the build command entirely, but in light of your comments, I'll leave the current build system unmodified (or provide an easy way to switch back to it).
Keep the comments coming!