http://en.wikipedia.org/wiki/Kano_model

The “Differentiating” quadrant corresponds to the “Excitement” features while the “Parity” quadrant corresponds to the “Performance” features (maybe even the “Basic” features.

Interesting is the fact it is quite common that over time (even during the project) features that were initially in the “Differentiating” quadrant are drifting into the “Parity” quadrant…

I think what’s also often missed is that prioritisation is time-based. When we ask ‘what are the must-haves?’, it must be qualified with a timeline. I.e., it must be clear that we’re not saying ‘if its not in the must-have category you won’t get it’, but rather saying ‘you won’t get it in this time frame’.

There is also a sequence/order aspect: its not that you won’t get ‘should haves’ at all, its just that you’ll get the ‘must haves’ first. And within those categories, there’ll be some internal order.

There’s also an example in Goldratt’s The Goal where a staggered delivery of a large amount of product is more optimal than a ‘big bang’ delivery of the same amount; more optimal for both the customer and the supplier. I.e. ‘we can’t give you all of this on this particular date, but we can give you some of it earlier and some of it later. Which would you prefer earlier and which later?’