As an Index controler and Pico user: The back straps are pretty much essential for any serious use; the controller purportedly includes finger tracking (capacitive) but you can't really open your hand without dropping the controller unless you have the strap.
If as I currently intend I end up purchasing this device, I will definitely endeavour to obtain the controller straps as well as the top strap for the headset at the same time, and I recommend others do the same.
I only own Index controllers, not the headset. I have a mixed tracking Pico 4 setup and wireless functionality is definitely one of the pluses; the higher resolution panels also make a significant difference (the Frame and the Pico 4 seem to have the same resolution). This is basically an open Steam-backed Pico 4 that's superior to my hardware and definitely superior to the Index. Here's a comparison:
The 1000hz tracking frequency is from the Lighthouse tracking system, which the Frame loses. For that and other reasons, I am not convinced the controllers are better than the Index controllers. Personally I think it's likely I will keep using the Index controllers, since I have the whole lighthouse setup and I own trackers as well.
Wireless, weight, no lighthouses, standalone use, more polished rendering. It won't be prefect, but it'll be a heck of a lot better experience than what came before.
If as I currently intend I end up purchasing this device, I will definitely endeavour to obtain the controller straps as well as the top strap for the headset at the same time, and I recommend others do the same.