What's in it for us?
At the moment the take up for mode S in the UK is very low even in the light of it becoming mandatory. This is because the fitting of mode S is of no improvment to the way we fly.
In the USA the GA community is fitting mode S but it is NOT mandatory............. why ?
It is because with the mode S you can get weather radar data link, traffic imformation and soon ADS-B (it's on the east coast now).
If the CAA want us to spend about £5000 per aircraft to help them out then we must have something in return and ADS-B would be a good start.
I do however wish them to note that some aircraft will never have the electrical systems to support any form of mode S, these aircraft are the types that only fly on good VFR days so ADS-B would not be too much of an issue.