We have a 40' one with a single rank, it is an awesome machine!!!!!!!!!!!!!!!  The only mods that I would really recommend if you buy one are Tompson closing wheel and d-cup diffusers. The diffusers let 100% of the air out of the line when the seed gets to the boot so the seed can fall into the ground.  I am running at high air pressure and the seeds really do just fall out when you go back there and turn the wheel.  I actually have seen guys put liquid fertilizer on these, some actually put the tank on the machine.  I personally would not put the tank on the machine because then it would be harder to get to the meters.  Also, scales are a must!  It makes it much more simple to calibrate.

Here is a pic of the Tompson wheels, they do a much better job of closing the trench IMO.

A few more pics......

If you have any more question feel free to ask.