I already have 3 Withings (2xSteel HR and since last week 1xSteel HR Sport) plus the Body+ health scale. I am very happy with the quality of all products. I also find the Health Mate app very functional. My previous watch band was Garmin (here I had 4 devices). The reason for going from Garmin to Withings is that while Garmin offers many more functions and the app is much more complex, in daily practice they rarely function well and I always needed to spend time with re-synchronization or resets. Withings is much more no-nonsense and in the end is much closer to what one really needs also in terms of trainings. However, as I train for the marathon and I run anyway regularly both indoor and outdoor I miss one important feature on the Health Mate app: the possibility to sum up the running distance per week, month and year. In other words, I would like to see in a graph how many times did I run every week and the total number of km, every week, every month and every year.
The other thing, there appears to be one bug in the app: when you select indoor running there will be of course a difference in the end between the distance shown by the watch and the real one measured by the treadmill. That is normal. When you try to edit the distance and correct for the new one, you can do that but after saving the corrected distance it will revert back to the original one measured by the watch. Because of this you can never correct for the real distance.
And for rest, you have great products, I enjoy the style and the functions, try not to overcomplicate them with unnecessary features (a second time zone feature would be great though). When they become too complicated they do not work anymore. Good luck!