I actually find the daily Bing image great. It is a nice counter-point to Google. It loads fast here and the UX is minimalistic but has a nice beautiful or inspiring background image every day and I don't mind that. It makes Google feel too primitive in terms of UX. As long as search is fast and effective it doesn't matter.
One thing that would be even more cool is an even more fine-level background transformation, like a background that changes every minute or less - from some location on earth. It'll happen.
Also, the muscle memory argument is negated in the same sentence due to the fact that you can set a default, so muscle memory doesn't really have anything to do with the choice. I as good as never type in google.com anymore, just use the Chrome omnibox.