I actually find that Spotify is a good example of a well made JS desktop app:

_ I used it on Windows, OSX and several Linux distros and really like the fact that the experience is the same everywhere.

_ No notable performance issues even with modest configs. It's been always usable in my experience.

_ Install size is on par with its competitors

_ Never noticed battery draining but I'll probably keep an eye out for this one now that you made me think about it :) I really doubt that a normal user would notice a difference.

Concerning code maintenance, it would be interesting to hear the opinion of someone who worked on such a complex desktop hybrid app.