This question has been spun off another thread that revealed that for SDK 1.2 you need to use a DTL-1/DTL-4 compatible BT card, e.g. the Socket CF card version F, but for SDK 2.0 you cannot use the Socket CF card version F.
So why not go directly to using version 2.0 SDK and buy a compatible BT card (whatever that might be)?
I can see that if you already have a BT card and is on a tight budget you would prefer to stick with 1.2 unless you have to use newer 2.0 features. Or if you are close to a release then you want to avoid the risk involved in changing your development environment.
But apart from that, can anyone see a good reason not to do the switch?