I highly recommend watching this talk from Rasmus Andsersson. One quote that stood out to me that I think rings very true is “your users come for the features, but stay for the details”. You can have all the features in the world, but if they aren’t well thought out, lack attention to detail or don’t work well together, then they wont stay long.

The following article goes into that idea in some more detail – “people will abandon your product for something that’s equally useful but more usable”.