I use a fitbit and was worried initially about the syncing thing. Though Google Fit is only a small amount behind my fitbit at the mo. Basically it's not getting my pottering around in the house with the phone stuck on the sofa but is getting when I've gone out with phone in hand/pocket/handbag.
The sync is a bit whacky though. Sometimes it seems instant. Other times its a few hours. Which unfortunately meant I ended up with an alolan egg!