I'm not a pro photographer, I am a hobbiest. I have other hobbies that I have found that spending less just gets you to want more, and ending up with buyer remorse. You end up with a consumer lense that doesn't hold its value very well that you need to get rid of to purchase this, spending more. So I just bought this knowing that I can easily get my purchase price back if I find I am in need of liquidity, or more lense than I bargined for. I rated the price a 10 because the price of ownership is very low for very high quality lenses, if you feel like an ass after spending $1100.00 for a glass filled tube, sell it to someone else for $1000.00 and you are hardly worse off. It is the complete opposite buying an old (or not so old) Brittish car.
I've been using this on a 10D with excellent results. The lense doesn't weight that much, I find it the same as having a 70-200 F4L around my neck. If you don't mind large zooms then you won't mind this, as it will be no different.
Just because you can handle the extra weight, doens't make the lense weigh any less, or become smaller. The lens will not fit in a standard D/SLR "triangle" bag space. I have a Mountainsmith Alpenglo backpack with a camera storage pocket accessable from the top, but this lens is to big to fit in it (the 10D is really tight anyway, while the 300D is perfect, but not with this lense). You will need space in your bag to fit a body with a zoom on it if you intend to leave it on when carrying it. I now have the Mountainsmith Lumin and it works great. Point is, the size affect more than just handling it on the camera, you have to fit it someplace when you pack it.
Also be wary of what tripod you have to work with. Just because you can handle the weight, doesnt mean your tripod/head can. Don't try and use rinky dink equipment with this on the top of it, being a dumbass isn't coverd under warrenty.
As far as the build quality, I am an engineering student and I see good and bad parts frequently come off of machines. People describe things as being "billet" all the time these days, and most people don't even know what it means and therefore use it wrong anyway. If it was sold on ebay it would surely be described as a Billet Canon lense. This lense is a brick. With it fully extended, its still solid. The dust seal on the end of the lens is a new one for me, but it is positioned well inside of the outer diameter so it will be highly unlikly to tear from normal use, and is is obvious that it is capable of doing what it was designed for.
I would recoment this lense to anyone. Its their decision to spend the money or not, and its not a black hole, you can get the money back.