There should be a setting to customize the bibtex entry when exporting.
For example, I really don't want local-url in my bibtex file. But I don't know how to get rid of it.
I usually don't need the abstract exported in the bibtex entry, either. Additionally, the auto key generation, which currently uses the doi, is quite unwieldy when working with the reference in latex. While I know you can manually enter keys, there really should be the option to generate keys in some simple fashion (i.e., author_year, or some such). For instance, the key generation in the old Papers application was quite reasonable.
We currently have implemented the Citekey generation. While this doesn't solve everything for this ticket it does solve the issue of citekeys being the DOI if that is not what you wanted.
Also, it would be really great if one could copy the bibtex record to the clipboard in addition to exporting it to an external file. That way it would be easy to append the record to the existing bibtex library (by pasting it), for example. Another option would be to append the bibtex record to an existing file.