I have driven a lot of Audi's with the CVT / Multitronic setups, and in my opinion, they are a horrible gearbox. I think they were just fitted to the two wheel versions - gearboxes in Quattro models responded totally differently. CVT gearboxes are like driving a dodgem! They feel very unresponsive, and the lack of a noticeable gear change doesn't give the impression that the car is doing anything when accelerating. I bought a few Audi's 10-15 years ago, and I avoided the CVT transmission because of the poor driving experience it offered (in my opinion!)
It is also imperative that the gearbox oil is changed religiously at 40k, otherwise the gearbox will soon need major surgery. This oil change isn't specifically highlighted in the service schedule, so was frequently missed if being done outside the Audi network, but when they were still in warranty, Audi were rejecting many warranty claims for gearbox issues if this oil change had not been done at 40k.
The Audi tiptronic is a good solid box, and drives like a conventional gearbox (like an Omega with a positive / distinct change). The S tronic box has lightening quick changes, which are still noticeable (a combination of the engine note, and the quick flick of the rev counter!) and I think is more suited to performance models.
I think the symptoms you are describing are typical of the CVT box, unfortunately.