Have had Vonage for 6+ years and like it, thought Magic Jack+ would be a cheaper alternative. Took them up on the free 30 day trial with a new number, (kept Vonage with the old number) worked as well as Vonage (which is great!) on short calls, but on call that exceeded 8-10 minutes (wife-daughter) the call would drop out. Tried Magic Jacks "tech support" online chat from India or Pakistan I think. Never found a solution, returned it within the 30 days was never billed.
Try the 30 trial, if it works, then its a good deal for you. Don't switch numbers untill you are sure it will work for you.