Are these sales people moving over from their old 360 systems, or is it that the new look and features, such as built-in WiFi and 5 USB ports on it (plus Kinect ready) are motivations for new people to get the new 360S model?

It's a mix of a lot of things really, but some will say; "It's all old 360 owners rebuying because of RROD."

I don't know.. I still wonder why I have 3 ps1's and 2 ps2's... and that was ages ago... I do wish I had bought another Dreamcast cause it dying... I can feel it...

It's a mix of things :

1. Adds new features.
2. It seems more reliable.

And the biggest point IMO ...

3. Staggered launch. 360S shortages in first couple of weeks. Then they restocked. Launched in EMEAA a couple of weeks after the NA launch. And then the 199.99 360S.

Think it is more that people that wanted a 360, but held off because of fear RROD are jumping in.

no more rrod, I would'nt be surprise if that is the most important factor other then the redesign

Because people see the new design as a final assurance that RROD is gone. Plus it's more silent.

First fire sale, then release of new slimmer more reliable 360, ( new and old will take advantage), then $199 version pops up a month later, once gain people take adavantage, next week Halo, then holidays, it's good times to MS and the 360 fans.

There is nothing really surprising going on, people are changing their 360 and now those who alaways wanted one are getting it.

Its a great console.  So a redesign reminded people of that.

1. Its cooler looking than the old model

2. Halo Reach and other big games

3. More reliable than previous models

4. More features than previous models