I coded a site with a large proportion of non-Ektron controls, but I used Webforms.MVP rather than MVC. This allowed me to mix-and-match MVP controls with the Ektron controls.
Ektron has got a couple APIs - there is an older web service based API which should be accessible from a non-Webforms project. I am not sure if it is possible to access the newer APIs (i.e. the non-web service API and the newer Framework API) fomr a non-webforms project. You would probably want to do a quick proof of concept for this to confirm.
The robustness of the Ektron APIs is a bit variable. Generally I have found dealing with simple HTML content to be good. Membership/login isn't too bad either. From memory, I've had problems with the more obscure components - eCommerce, Taxonomies, Blogs, Calendars. Generally, the problems include-
- Empty properties
- Lack of documentation
The newer Framework API (initial release in v8.0, covering Content and Folders, with a full release in v8.5, due in Aug 2011) is a lot easier to use, though I've still had occasional problems with empty properties.
Overall, as long as you're sticking to HTML content, you should be fine, provided you can access the API from a MVC project.