I have returned one Bionic due to the battery drain problem, the replacement now has the data connectivity issue. I use the app called "Restart Connections"
https://market.android.com/details?id=com.dazbradbury.restartConnections&feature=search_result
It works really well to restore the data connection, but usually just the 3G comes back. It takes awhile for the 4G to come back. I am currently waiting for my third Bionic in hopes that the third time is a charm...We will see.
UPDATE: I got my third Bionic yesterday and it has stayed connected consistently to either 4G or 3G when transitioning between each. No data signal lost as of yet. I have been using it heavily to try and get it to drop again, but so far so good...I will update again if it happens again. Guess if you continue to return these you might end up getting a good one.