Well, to me anyway...
Difficult to decide where to put this, but as it's not really practical if you don't use ADSL, I thought here would be appropriate.
BT have launched a 1571 Online service, whereby you can check calls in your 1571 voicemail. It will display details of the caller, but can also play you back any messages. Handy when travelling.
Sorry if you all know about this already (in which case, why didn't you tell me? :) )