1- BANDWIDTH SAVE: ThunderADS users will save only 33% of their links in comparison with paid ThunderCache plans, you can follow this loss by access.log file any time when ADS_HIT_SKIP appears.

2- PREMIUM: ThunderADS users can't use Premium Accounts.

3- CLUSTER: ThunderADS users can't use Cluster Mode.

PS: ADS works only in rev 919 or later!