We have been experimenting with -- but have not yet implemented -- the Ebsco chat widget. The normal embedded widgets seem to work fine; the popup widget also works. Haven't tried the followme widget.
There are a couple of limitations:
Ebsco widgets only appear in search results. There's no option for having a widget on the start page or in item records.
There are several Ebsco-created widgets that always live above the library's custom widgets: this includes at least an "AP News Wire" widget and a "Related pictures" widget. Both of these can be disabled -- the newswire one seems manifestly useless to me, but depending on your user base there may be a call for the "related pictures" one. But both of these push your widget down on the page, so bear that in mind.
Also, the widget panel is always on the right.
That's about all I can think of for now. As soon as we come up with some language and graphics for our popup widget button, we're probably going to just go ahead and implement it.
As for your first question: I don't know whether it can be turned on database by database. That might cause some interesting problems when you do a cross-database search...
Overall Ebsco has been very responsive with letting us try different things in a test implementation, so you might contact your representative and ask about getting a test environment set up.
That's it for now!
-dre.