Mind if I list some useful stuff that made me use mendeley instead of bibtex:
1) it can export the whole library as bibtex
2) right click over your paper -> "copy citation as tex" -> paste it into your latex file.
3) keep the PDF together with the metadata
4) anotate the PDF
5) search those annotations
6) put DOI, PMID, ARXIVID -> get all metadata from the interwebs
7) organize it with keywords, collections
I can't believe it's better to keep a text file edited by hand than to use an user interface that automates several things. "Better", at least, in the saving-time-and-not-getting-mad sense.