Can you tell me how far is "islet cell transplantation" is successful for type1 diabetic , what are its side effects?

Still experimental: Islet transplantation holds promise, but is still experimental. You would need to be on anti-rejection drugs, which have side effects, so pancreas / islet transplantation is only done in conjunction with another transplant, usually a kidney.

Need for ISDs: Islet cell transplant recipients need to take anti-rejection meds to prevent rejection episodes. Another major issue is that islets do not seem to live more than several years.