I was once sceptical of people saying how important geo was.
With my MX5 its really made it clear though, when I bought it tramlined horribly in the motorway, and didnt feel stable at all.
It had been set up at 'wheels in motion' at the same time the lowering springs went on, but I checked the invoices and this work was done 18 months prior to me buying the car and hadn't been checked since, so I thought it would be worth looking at.
I then had powerstation look at it on one of the Beissbarth alignment rigs, they discovered it was really a bit wonky after that length of time, and they put it back to the settings it was meant to have according to the WIM printout. After this it was soooo much better, more planted, better turn in, more stable and just better to drive all round.
I had planned the same for my S2000 as everyone says how important it is for them to handle properly, sadly a bit of over exuberance, cold wet road and a road sign meant I never got round to it..!