I think this new MP3 tab is great.
There is one thing I've noticed with the version of lame_enc.dll that comes with BeSweet (and 3.96.1 from Rarewares too) that I think people should be aware of:
For some reason it sets the minimum bitrate for the -V modes to 128, where as the command line version only does this for -V 2 or lower. This means when you try to use a low quality you often end up with what is effectively a 128kbps CBR file. I don't know whether this behaviour is intentional, but I always use -b 32 with -V modes greater than 2 so you end up with lower VBR bitrates like you get when you use the command line version.