I recently broke a side rail on my Smart Trac, and found that the new replacement ones are aluminum instead of plastic. So obviously somebody has addressed the "design flaw" mentioned in other reviews.
This is a great rudder for racing, allowing tight buoy turns and cutting inside other boats, and it appears to be much lower drag (and quieter) than the flat plate rudders on my team-mate's EFT. It hasn't been great for me on a trailing surf once the waves get faster than I can paddle, but I suspect that's more a boat issue than a rudder issue.