Networks won't change to MicroSIM until phone manufacturers utilise it in their new handsets, as it stands afaik only the iPad and iPhone 4 will be using them. Albeit, that's a large market, it's not enough. Especially since adapters are relatively cheap and you can just cut your current sim down to size.
For those buying the PAYG handsets, it's an easy switch as CS will port everything over from your old SIM. Then just buy an adapter on ebay for 99p so you can use the MicroSIM in any other phone.
For those buying the PAYG handsets, it's an easy switch as CS will port everything over from your old SIM. Then just buy an adapter on ebay for 99p so you can use the MicroSIM in any other phone.