When determining in which type of document you want SP inserted, you should always consider the extra load on one's processor that some languages -like Flash- imply. Inserting SP inside a heavy Flash interface is entirely possible but should be done with care performance-wise. Furthermore, keep in mind that users with newly formatted machines will most likely have no plug-ins installed when getting on your website and that combining several plug-ins will induce the installation of each of the plug-ins used before a given user can access your site entirely.
However, it is entirely possible to create completely interactive lay-outs with SP embedded inside. You can for instance replace almost all the functions on the skin by your own Flash buttons or images and lay them out as you want inside your document.