So....I'm very happy that GC has fixed the syncing issues with MFP. And it has been fine for the past couple of weeks...up until a couple of days ago, when it started posting activities to MFP twice (if there are multiple activities being synced at the same time - ie a bike/run brick - only the first activity posts to MFP twice). Activities are only posting to Strava and MapMyRun once, so it appears to be strictly a GC/MFP issue.
Just wanted to make the GC folks aware.