I shall give Teamviewer a go and see. Its fairly pricey[1] at £439 but at least it is a one off payment unlike many.
[1] I am assuming the free one is only free for non commercial use?VNC-SC (until recently) was very slow when controlling vista or Win7 boxes. It was indeed like getting a haircut by post. The most recent version however has managed reasonable performance on all platforms and also manages to run at elevated privilege so it only pops up a UAC confirmation at the start, and does not hence loose control by incurring one later.
The preconfiguration bit is quite handy I find however in that I can brand it as I want and then have a number of options presented to the user so I can select where the support request is directed (i.e. to me and in which case which of my computers, or to a colleague etc). Its certainly not perfect (I would love an ability to have it survive reboot for a control session so that you can reboot a machine and then resume control without user action at the far end)