If you have a 22" LCD monitor, it is not just worth it ,but essential. When I used the VGA output, it limited screen resolution to 1680 x 1050 (native) and 16:9 ratio (black bars).
When I plugged in the HDMI cable, I had the same problem at that resolution. Needless to say I was disappointed. Then, something told me "go ahead and select 1920 x 1080 and see what happens". Lo and behold, my monitor scaled the picture PERFECTLY to 1680 x 1050 with NO distortion/bluriness and there are no black bars!
I have an envision 22" widescreen LCD with a hdmi->dvi adapter. I bought a $30 HDMI switch from Radio Shack, 3 inputs for one output and I can switch my computer and the xbox 360 easily...