They were massive amongst the group people I hang a round with as a kid, I had cheap Halfords (Trans-X?) ones in silver, always wanted some Shimano carbon ones. Thinking I may get some for my XC bike for nostalgia purposes.
i have one on my kili pro magnesium, so much flex in that frame they should have one built in.
you can get new (or at least nos) cnc ally ones on ebay, various colours, and the carbon shimano ones are often on there too.
Any rim brake will benefit from a booster because instead of wasting energy spreading the stays, energy is used squeezing the rim. The problem people tend to have with them is just aesthetic, and weight I suppose. If you like the look of them and aren't that bothered about an extra 60 grams or so, you'll get better brakes if you fit them
Odyssey, though is different to the one in that review 'labortest' posted (looks more like the one next to it). Also help stiffen the Mag21's as works in conjunction with the fork brace, may also make them last longer as they're not twisting the lower legs as much