Yes, IMO it just formalises what occurs already, and puts a very tight timeframe on the request, which I support.

I imagine it will be pretty much the same type of buyer that seeks a cancellation straight after sale, maybe a few more, but they are not really the buyers that many sellers want to do business with anyway.

I like that the new system will put the onus on the buyer to request the cancellation, and that the seller will be in the drivers seat in terms of agreeing and the timing of agreeing, instead of the way it has been, with buyers requesting cancellations and then a number not bothering to respond to a cancellation sent by the seller, so the seller has had to wait it out 7 days, until they could relist. 

Or in the worst case scenarios, a buyer requesting a cancellation then refusing it when sent by the seller, meaning an unpaid dispute could not be opened.

Good move eBay.  Thank you.