The reason I want a frontend is to launch the emulator via a batch file so I can activate an AutoIt script to resize the emulator window.
Let me explain why: when running low resolution console games on a 19" computer monitor it looks horrible. It is way too sharp and blocky looking. Also, the console games are sometimes a weird resolution that doesn't fill the screen entirely. MAME handles this nicely with hwstrech, but other emulators don't handle this well. I've found, however, that with Gens, NNESTERJ, PCAEwin, and Intwin that you can run the game in a window and resize the window to the whole screen. This not only stretches the game nicely to fill the entire screen, but it performs some sort of filtering or smoothing on the image so the low res games look nice. The only problems are that I don't want to bother resizing the windows every time I run a game and you cannot resize it larger than the screen so you still see the title and menu bar. I can't stand seeing any trace of a window while playing a game. I know that AutoIt can resize and position a window even larger than the screen (I do this on DVD's to zoom in on letterbox titles to reduce the black bars) so all I have to do is call a batch file that launches the emulator with the Rom and calls AutoIt to resize and position the window to make it look fullscreen (window borders and titlebar are off the viewable portion of the screen).
The frontend will also hopefully give a nicer looking Rom list than the ugly windows open file dialog box and show screenshots.