Dual Sim modules?

[BigPappa]

has anyone used a dual sim module with UK networks? The idea appeals to me to carry 1 phone instead of two but how does it work? Can you hot swap between the networks?

[Ricardodaforce]

Seen this? http://www.gsmarena.com/samsung_d880_duos-2156.php

[threadkiller]

the newer ones are not as good as the originals, they tend to involve cutting your Sim card down to fit in a holder. switching between sims tends to involve switching the phone off & on