Very positive from what I've seen. Varying degrees of preference when it comes to the Joy-Cons free or in the grip vs the Pro Controller. UI is fast and snappy, hardware feels very high quality. Battery Life is solid, BotW draining in 2.5 to 3 hours depending on settings, much better than 3DS when in sleep mode drain, only 2% drop after 8 hours. Overall they've all sounded very upbeat and positive about the system. Even with known stuff like no video apps, browser, VC at launch and such.
That is really good to hear.