Regarding stability, the ballhead is stellar. The tripod is a very lightweight design so while the three legs seem to be doing a good job with the centre column down if I raise the centre column fully and then give my 200mm zoom a tap the vibration is noticeable and takes around a second or two to die away. Things are much better, as you would expect, with the centre column down with a much higher frequency of oscillation at much less amplitude which seems to die down in under a second after a tap. That "tap test" with the EF 70-200mm f/4L IS USM was done with the camera's plate (a Kirk Photo PZ-120 designed for the EOS 40D) attached to the ballhead. I'm not sure a lens plate would help as, while the camera plus lens would be better balanced, the ballhead is easily able to cope and the same mass is still oscillating on top of the column.
As you noticed, this isn't the cheapest kit in the world, unfortunately. With the ballhead the price buys quality engineering, in my opinion, and it's worth every penny. With the tripod the price buys the light weight and compactness that high-tech four section carbon fibre legs offer. Obviously it can't be as stable as something three times its weight and twice its bulk but I have one of those and there's no way I'll cart that up and down the hills on my back! However, using a cable release and with my backpack hung from the centre column some initial pixel peeping looks encouraging and I think it will be stiff enough. The really severe test, though slightly unfair given I bought the tripod for landscape shots, will come with, say, a one second exposure at 200mm and with mirror lockup either enabled or disabled.
I need to do a bit of planning for those shots, rather than ad hoc tests in the garden, so that I can get a good idea of just how good, or bad, the tripod is.
, That's a great recommendation if you end up buying the same kit twice. Which model, if I may ask?