(Download the script from this article flac2mp3.sh)
When converting FLAC files to MP3, the first problem you will notice is that lame does not support FLAC files. This might now seem like big problem, because you can easily decode FLAC files using the command line tool flac and then use the decoded file with lame.
The real problem is that you will loose your metadata in this process, so the tags you added to your FLAC won’t be copied to the MP3 file. While you could “easily” add them by hand, it is pretty annoying to do that even if you only want to convert a handful of files.