Yeah, I know what you mean about XSL; as far as I know, the XSL syntax component of the HTML sugar defines the syntax zones for coloring, but doesn’t provide any codesense.
MacRabbit is Jan and Lenaic; early progress on the app has been slow because they’ve both had their time divided by graduating from university. If I recall, Lenaic should be in the clear by this point, but Jan won’t have discharged all of his university responsibilities until August. We all keep hoping that the pace will pick up (or that Jan and Lenaic start taking a more active/communicative stance toward their community, which would help discharge a lot of the frustration at perceived lack of progress), but so far no dice. For some of us, like myself, the current strengths of the software make it worth using anyway (and continuing to work to improve through Sugars). For others, Textmate or Coda are still the better options.
Even if you switch over to another app in the short term, I don’t think your investment in Espresso will be wasted. Like Coda, Espresso has had a rough time getting off the ground, but I also expect it to hit its stride a few major version increases in (1.5 or so will probably be the sweet spot). If the app’s shortcomings are interfering with your workflow/happiness too much right now, definitely don’t bash your head up against it too much; send MacRabbit your feature requests, and switch back to Textmate or Coda for the time being.
Definitely let folks in the forums know if you have any questions about working around Espresso’s shortcomings!