Gmail Promotions Tool

Hi there!

I'm doing CRM for DR SMILE and was tempted to leverage Gmail Promotions Tool for our discount campaigns. As far as the documentation is clean and easy to implement the troubleshooting is a mess (sometimes it works, sometimes not, preview in the Google tool differs to what I actually see). Also, from what I read it's pretty much impossible to track performance or A/B test that feature as it's functionality depends on many factors (app version, where your email lands, are promotion tabs even enabled, are you going into top picks). 

I was wondering, does any of you have a positive experience with this feature or can share any tricks to improve testing of it (I went through the whole troubleshooting page from Google already)?

Many thanks,
Gosia