If you are talking about the bolt on extensions, I wouldn't trust them, your ass depends on that thing holding up good. But if you are talking about an extended swingarm (the whole arm) then yes they are good when you start increasing your horse power. The more power you have the longer the swinger needs to be to hold the front end down, but you also loose traction with the longer swinger which is usually compensated by with more paddles. It really depends on what type of riding you do and how much modding you have done to your bike. PM Loco, he puts out some pretty good swingers from what I have heard..............
By the way welcome to the HQ and the addiction................