Good: heavy duty commercial quality unit
Bad: Does require you to cut and modify your existing mower deck
Ugly: My unit is painted black and my mower is red. Wife says it is not color coordinated
Quality of cut: can't really tell a difference between the flex deck cut and the cut of my Toro 36"
Maint. Requirements: Sharpen blades and grease same as main deck on mower. (Flex deck easier to change blades/ flip deck up)
Longevity: Only had mine a year. Comes with warranty/spare parts
Overall Performance: Cut my trim time by about 25%. My setup mows 54" but fits thru gates around 37". And saved the day when my 62" z broke a belt, cause I was able to finish up mowing.
Brands available: I have Flex-Deck brand, probably the only add on brand (also carried by Dixie Chopper) and I think Howard Price Turf Equipment makes one that is permanently attached to their deck and only available in a 80" Z version