Have this lens, and it's been pretty good to me so far haven't experienced any of the "softness" ADMA spoke of, except when it was due to user error (me).
Here's one with the macro slide switched:


and one without it being in macro mode:


Do be aware that the macro switch is a little cheesy, you can only switch it on when the barrel is fully extended (275-300mm range) and it gets *stuck* from time to time. Work the zoom back and forth a few times and try it again (that usually does the trick)