There's an article in this month's American Iron about them. Seems like a pretty good setup. Unfortunately, it's pricey. The pulleys, belt, helical gears, and cam plate will cost you around $1350, then add about $350 for your cams. Got the prices off of the web.

I was looking at possibly going this way on my SEEG so I was also researching prices. Your figures are the best out there right now, and they represent a
significant premium over a regular gear drive setup. With the options I would want (helical inner gears, chrome cover) your looking at around $1700 not including new cams. I was also concerned about using Wood cams, since they are known for high lift & short duration with extremely fast ramps. This tends to create excessive noise and valve train wear. However, if I read the info on the Wood web site correctly, you can use other companies cams with the belt drive
as long as you're willing to stay with the chain for the inner cam drive. The whole idea for me is eliminating the chain and tensioner, so that option isn't worth considering IMHO.
The biggest advantage I see with the belt drive is the ability to tolerate a little more pinion shaft runout than the gear drives. Maybe if they decide to get competitive on pricing I could see going that way, but I'm too conservative (cheap) to spend twice as much for an unproven system over one that's been around for awhile like the S&S gear drive.
Jerry
KNIGHT PROWLER SILENT BELT DRIVE SYSTEMS
PART # APPLICATION / DESCRIPTION LIST NOTES
*
WBG-1 2000 -2006 T.CAM W/GEAR DRIVE $1,340.00* WBG-1-06 06 TWIN CAM DYNA & ALL 2007 GEAR DRIVE $1,340.00
*
WBC -1 2000-2006 TWIN CAM INNER CHAIN $1,275.00* WBC-1-06 06 TWIN CAM DYNA & ALL 2007 INNER CHAIN $1,275.00
ALL MODELS COME POLISHED WITH SOLID END COVER
OPTIONS
CHROME PLATING $85.00CLEAR LEXAN COVER W/ HOLDING RING $75.00
WH-1 HELICAL INNER GEARS $260.00
TOOL KIT.. INSTALL AND REMOVAL $50.00*
1999 THRU 2001 EFI EXCEPT 01 SOFTAIL & 99 THRU 2000 CARB WITH CAM POSITION
SENSOR USE " P " REFERENCE... 1999 EFI W GEAR DRIVE USE PART # WBG-1P
APPLICATION NOTES
YOU MAY USE ANY MAKE CHAIN DRIVE CAMS WITH OUR KNIGHT PROWLER BELT DRIVE SYSTEM.
WHEN USING GEAR DRIVE CAMS, YOU MUST USE KNIGHT PROWLER GEAR DRIVE CAMS MADE
FOR THE KNIGHT PROWLER BELT DRIVE SYSTEM!! OUR CAMS ALL ROTATE CLOCKWISE.CONTACT BOB WOOD FOR TECH INFORMATION REGARDING OUR NEW " SILENT HELICAL CUT INNER GEARS "