So you consider what's been spewing out of Redmond as MS dedication to the platform? I see nothing that differentiates today from the past other than the OS and WPs state in the marketplace, and considering where the latter stands I'd say that says a lot about their commitment. In the past we had Samsung, Acer, Hisense, Alcatel, HTC, Huawei, Blu and many more, so I see nothing about those who chose to step back into the ring as being a reassurance of Msft's commitment.
Then we get into the quality of updates, one can use what ever excuse they want (Alpha, Beta) yet some of them should have never left the playpen period. If this were anyone other than Msft I can guarantee you that people would not be labelling that company as being "committed", and that's a fact. As for continuing to update the OS, releasing insider previews, well those who are doing the testing and reporting need some sort of payback as its well known Msft is not doing the majority of in-house testing.
As for the store, if you are not experiencing anything you'd consider out of the ordinary then either I'm a one-off or you are willing to tolerate a whole heck of a lot more than me. I usually run Public Releases and sometimes Release Previews and every single time the store has become another thorn in my side, sluggish, errors, lacks much info, clunky interface, etc. Suppose if you've acquired all your apps, set them to "auto update" then never have to delve into the store you wouldn’t be aware of them. All in all I find it a pretty lame attempt by MS which far from radiates "commitment".