I'm not on Win10 - are UWP apps still slow and clunky? Like they don't really act like normal windows? Still tablet-optimized or whatever? Last I checked on the W10 beta calc took several seconds to launch. (And had far less features, like no editable history.)
MS flubbed the launch and followup on Metro so hard (not to mention the shitware on the Store) it's really, really, turned me off from using or playing with it.