Tried out Signal yesterday. It's a dedicated media remote controller, and is limited to media control. Remote Buddy (RB) in addition delivers interaction with your other applications, though best executed through use of the Apple Remote, or when you use the Apple Remote simulation through RB on iPhones/iPod Touch.

I have used Remote Buddy as a Media Control, and have been quite satisfied with it - particularly after it got multi-room control, something which Signal has had for quite a while, as I understand it.

Setup is easier with Signal. You get the URL you're supposed to enter in the browser of the iPhone/iPod Touch displayed on the screen of your computer, after you launch Signal for the first time. Just enter that URL in the browser, save it as a bookmark, and whenever you recall that page, you're ready to control your media.

With Remote Buddy, you have to go into preferences, find the URL and enter it. Not much of a bother, but Signal's way is faster.
 
I also suspect that Signal is faster overall compared to Remote Buddy. The latter app is waiting for a variety of different commands and user options, where Signal does just one thing: media.

When you switch between albums on Remote Buddy, the transition to the new cover is near instantaneous, once the app has gone to the new album. With Signal, the app goes to the new album, starts playback and then delivers the cover to your iPhone/iPod Touch. Overall, I found Signal more responsive - though with a few glitches as described below; occasionally I have had Remote Buddy requiring me to relaunch its browser page when it's jammed up, I haven't used Signal long enough to have come across such a freeze. My experience is that any problems with RB are resolved by closing the browser page and relaunching it, and expect that Signal will behave similarly.

Of course, I've had Remote Buddy for months, and Signal for a few hours. Could well be that I'll find that Signal will also go dodo occasionally. I did have a few glitches where playback initiated by Signal was interrupted when I went to another page on the computer's browser -- but I can't really understand how that should affect wireless playback of sound, so it may just be a strange coincidence - it did happen a few times, though, and has never happened with RB.

Overall, I'd say that Signal like RB is an excellent app, and maybe better than RB if what you want to do is just control media playback on your computer. Easy to get going, works with both Mac and Windows (!), and provides snappy control of the essentials with no freezes experienced so far.

I know Peter's found RB to be slow on his setup, and he may want to try Signal!

http://www.alloysoft.com