The deft i have (not 100% sure of the model, isn't the "huge" one) has some things that annoy the heck out of me. But it seems nobody else minds these, so possibly ideosyncratic. The buttons are weird and small, like the right click iirc is about 5mm in width. My fingers dont happen to sit on the very narrow operable surface so it is so akward. I have no idea why make buttons like that. I find the scroll is inconsistent. And you need to replace the batteries.
If you are happy with the device you have no reason to buy more stuff. But if you need another one this is like half the price, is more comfortable and more functional. I think future is totally unknown tho; i am not optimistic about official support and so far its too new for even community information.
I have the impression these are basically disposable. However logitec recently has created some relationship with ifixit so perhaps there is some chance to salvage them. Especially if you have a bunch of differently-broken devices hanging around.