There's the tricky part... Getting all the taps going. I built a 6 tap kegerator last November to replace my defunct 2 tap setup. I finally got my sixth beer on tap two days ago.The holes were drilled 3" apart. Now that its together 4" would have been better.
Just have to be creative when I make my tap handles so that they are not bumping.
If you wanted to adjust do a re-drill and fill the old holes with dowel pegs. A little putty and sanding. The tap handles don't look like they interfere with each other as is, though.
Nice build. Now you need to get 4 beers on tap.