Iam using this dual sim holde from ~6months..and this is the model in which we have to cut the sim card..
when u put the 2 sims of ur choice in the holder and place the sim holder in the mobile, a new sim applications menu will appear through which u can change the operator.
I tried this in Nokia, Motorola and sony ericsson. It only worked in Nokia.
And sometimes(very very rarely) it shows the message "Sim card registration failed". For this u just have to change the phone to "Offline" and the back to "General/silent/whatever u want".
Overall it does its job pretty well.Also that operator switch time depends on your mobile operator also!
Intially i used Reliance GSM sim and it used to take ~45sec to switch from vodafone to reliance..but Airtel and Vodafone take only 15sec to switch.
And yeah u can use all the features like GPRS,SMS,MMS,etc.. from both the numbers
infact i use the Airtel SIM only for GPRS and Vodafone for other stuff
Regarding SIM cloning, it is not possible with the present generation SIM cards. I have done a good amt of research in it and found that the SIM which were made b4 1998(apprx and again depends on operator) can only be cloned.
And i suggest you to get the SIM Sim holder from other countries like China/Hongkong or u can buy from the site :
Vavolo.com! Professional Cell Phone Accessories And Data Cables
Hope it helped