There are two main issues for me with the GTW plugin:
It does not pull in Attended OnDemand status info from GTW. We make our past webinars available on our website, and I'd like to capture stats from that in the original webinar to show a more complete ROI on the webinar.
It does not support Series and Sequence creation types from GTW. This caused a real problem recently. Not knowing this was not supported, I created a Series webinar (one webinar, 3 dates, bc when the webinar content is the same, that's substantially easier in GTW).
I then created my events in marketo, and lo and behold, each date instance showed up in my list, implying that connecting to that webinar date would, in fact, populate my registered, attended, etc status field as the plugin does for single webinars. I happily created my reg forms, again thinking it would all connect up as usual. Not so much.
I had to go MANUALLY transfer registered folks from Marketo to GTW (and no, I could not just re-create the webinars as singletons bc my sales team cleverly found the GTW reg page and sent that to some customers so I had registrants in the GTW webinars - which I had to manually transfer back into Marketo), then after the webinars, manually update the attendee statuses.
This should be an easy fix if the connector is set up as I suspect it is based on this behavior: Instead of keying on only the Event Login field (which is the same for all webinars in a series or sequence), key on either the Event Number (unique to each instance of the webinar) or a combination of these two fields.