NOTE: like Rollyo Google CSE searches in the HTML, not the feed content.
You can share your engine with others, add a site to your search engine via a bookmarklet, and add it as a widget to your start page or blog sidebar.
In the advance section you can upload an OPML file, as mentioned here and the link above it would be even better for the Google CSE to subscribe to this OPML. In the future when you add/delete sites from your OPML, it will automatically delete/add from your Google CSE. But I suppose my OPML Reading List from Technorati Favourites contains feed URL’s and not home page URL’s, but still it could perhaps discover the homepages from the feed URL’s.
In fact when you upload an OPML it does discover the homepages by looking at the htmlURL tag, see more:
“We currently accept OPML files such as those generated by Bloglines. The value of ‘htmlUrl’ attribute from each ‘outline’ element is added to the list of sites used by the custom search engine.”
Still I wish you could upload a URL instead of uploading a file, at the moment if I change my OPML, I will have to save it as a file and upload it to Google CSE. Instead if my initial upload was a OPML URL (not a file), then I would never have to worry about again as it would automatically update, as it is subscribed to my live OPML.
Here’s a how to on creating a search engine from your Google Reader OPML. But as mentioned in this article the moment you change your OPML, you will have to reload it in Google CSE.
What a hassle I’m adding/deleting feeds constantly, they should take a look at BlogBridge and FeedBlitz.
Also see how to use it to search your del.icio.us account.
One thing it lacks is the search menu that Rollyo offers, although Google CSE allows you to make multiple search engines, you can’t get one box where you can choose from a menu of which search engine you would like to search.
Imagine that possibilities this would have with OPML, you could upload an OPML that has lots of other OPML’s within it (OPML includes). Once uploaded you could use Google CSE to search the OPML, or one of the includes…kind of like being able to search your whole RSS Reader or just within one folder.