This was also the first time I used K2Store. There were a few updates to this plugin for JoomlaWorks' K2 for Joomla 1.5 while I was working on this project, and I got some excellent responses from the creator of K2Store.
The greatest difficulty was that the delivery charges that needed to be calculated before payment was made via paypal were a little complex. It was based on how many pairs of foldable flats the visitor bought.
I can calculate the delivery inside PayPal, no problem, but I need the calculation and addition of delivery charges to happen before the PayPal gateway. K2Store unfortunately doesn't support this yet.
The clients are soon adding more products to their website soon. They are very happy with the design and my use of their very straightforward style manual.