I haven't found a better system than the MC519.
IB HAPPY with mine.
That's quite a set of rants. Just to balance that out, the MC519 I use on my 455 (got it used) has been flawless - easy to attach and detach, never comes off when you don't want it to, tilts and dumps easily, does a nice job picking up leaves and pine needles.
As the first poster found, having the right parts and attaching the unit properly makes a lot of difference - maybe those who are having trouble should check and make sure they have it set up correctly.
Tim