I have the Kerker 2 into 1 header on my 03 Deuce and like it.
Have been running it for about 2 and 1/2 years now. It performs well and has a nice deep rumble. Really barks at higher RPM. My only complaint would be noise level, it makes a pretty loud rumble at freeway cruising speeds. This is good is safety reasons, the traffic knows I'm coming and they normally give me the right of way. But after a long day on the road the loud exhaust can get a little too much even with ear plugs.
For this reason, I'm going to change the muffler on my header to a SE tunable (Supertrapp) system.