I have been using InSync for Google Drive for the past 4 years. Been pretty happy with the performance. There is only one catch with their personal license: you

I have been using InSync for Google Drive for the past 4 years. Been pretty happy with the performance. There is only one catch with their personal license: you can only use it for the account you bought it for. Changing account implies buying another license. You can't sign on more than one Google account as your main account - although they have some child account configuration & you could use it on as many computers you want.