I am having problems installing CoolCommerce on my EE install - however Kevin is hoping to get out a new version this weekend to fix the issues. The good news is that you don’t need Coolcommerce to run FoxyCart (though from what I see it is of course better with CoolCommerce). The bigger problem I think you will have, based on your user name of Stig I am guessing your from the UK, is the fact that FoxyCart does not have very good gateways for UK payments yet - they are working on it but the only option is very very expensive (£700 set up with £100 month costs +£7.50 Foxycart + the % the bank take from each transaction). Foxycart have said they will be looking into providing access to more affordable UK gateways (and so they should as it will encourage a lot more UK sites to use thier fab interface) when they have restructured their back end to make it much more flexible to allow all sorts of gateways to be integrated quickly - which makes sense.
So what to do? I am building a site right now with this problem and am hoping to get it live next week. I have decided, with the client, to opt for Romancart which is very good but lacks any real panache! We will be switching over to Foxycart if and when they have the UK part sorted, but until then real life kicks in and my client needs to sell products and Romancart will do it for them initially!