Hey Diana-
You should be able to do anything within the context of Marketo that you'd expect to be able to do otherwise for most website setups (well beyond the general use case of Landing Pages). I haven't seen many website built in Marketo but the technology is not limited in a way that you wouldn't be able to do most "web-stuff" from within Marketo itself. The template editor can be stripped all the way down to a blank HTML page, and built up from there just like any other website/page. The functionality isn't necessarily "bound" by Marketo, but there are some aspects of the Marketo-native functionality (like editing a page or section of content) that are a bit different than other platforms.
Maybe it depends on the type of functionality you're looking for, but I've worked on a few projects that were more like sites than Registration Pages and I think it would be possible to accomplish most things on the Marketo platform. If you've got an idea or some example (links) that you're kicking around, I'd be happy to take a look and let you know if something seems "out of range" for what I've seen.
I also think that if you found success with the Email 2.0 editor, you should have a similar experience with the Guided Landing Pages in Marketo. I think email is a "bigger jump" from outside Marketo to the 2.0 Editor than it would be from another web platform into Marketo LPs. The LP interface isn't as good (in my opinion) as the Email 2.0 interface, but b/c it's webpages you're able to do a bit more with the limited options in the Landing Page editor.
I'm always up for something new and outside-the-box to do with Marketo LPs, I'd be curious to see what you had in mind here!