I have one of the wonderful old Hobart KA mixers, some 30 years old and still going strong. I was intrigued by the new Beaterblade and ordered one to try it out. There's several different models made for various KA, Cuisinart, DeLonghi, and Viking stand mixers. It arrived, and I just tried it today with some banana bread.
All I can say is, I'm so sorry I didn't order this earlier! A week ago I was making cookies for a cookie swap, and this attachment would have made some of the recipes MUCH easier if I'd had it then. It really does work, scraping the sides of the bowl perfectly and making it even faster to cream the butter and sugar together.
Note that it is all plastic - even the attachment part. Don't know how long it will last, but I just wish this had been invented 30 years ago when I was really doing a lot of baking. Definitely worth the money, if you do a lot of cake/cookie baking.
And now there are two mixer blades on the market. The newest is the SideSwipe Spatula Mixer Blade, with a different design (see link below). Cook's Illustrated actually liked this one better than the Beaterblade that I purchased, but I didn't see the review in the Jan-Feb 2009 issue until afterwards. I'm satisfied with the one I got, though. The Sideswipe looks like it's more durable, but there's a lot of crevices you'd have to scrape clean. http://sideswipeblade.com/solution.html