Can REST like URLs be used in a Seaside application maintaining all references to continuations? That is, all good things of Seaside but with pure indexable URLs.
I am aware of the WARestfulComponentFilter in Seaside-REST, but if I start here will I be able to use the continuations, call, answer etc? Will it be worthwhile to give it a try? I just need to know opinions.
This depends on what you want to do. If you do not want to see the Seaside session and continuation parameters in the browser's location bar, then this is difficult to achieve completely. But it certainly is possible to build applications that produce indexable urls in Seaside. Perhaps the best place to look at an example is the source code of the Pier CMS.
Wether it is possible to keep "all goods things of Seaside" but use "pure indexable urls" depends on your app and what is in your session state. The session and continuation parameters of Seaside reference the actual session state on the server. If you want a url that references exactly the same thing (but is clean and indexable), you will need to communicate the entire state in the url. However, in most cases, you will not want to encode the user's session state in there. So, this is something you need to do yourself and Seaside provides the right entry points for that.
Lukas Renggli's presentation explaining RESTful urls in Seaside will give you understanding on how to create indexable urls. Getting rid of the _s (session parameter) can be done in various ways in Seaside 3.1. You can customize the WASessionTrackingStrategy or use one of the predefined ones (for example using a cookie). Getting rid of the continuation parameter in your app is more difficult: email thread on REST Urls in a Seaside app.
Finally, as mentioned in another answer, take a look at Seaside REST
In summary: generating indexable urls is possible (shown in the Pier CMS), removing the session parameter from the url bar is easy as well but removing the continuation parameter from the browser's url bar requires manual hacking.