Having healed since Launch I have experienced all the healing changes and in WOTLK mana was pretty much infinite even with the nerfs, so healing mostly was about throughput and not mana management. Having said that you was able to heal people through failed boss mechanics or trivialized fights in general. Take the twin valks in TOC for instance, it could have been a fun fight but instead with the over powering of healing you can just stack everyone at the door and and heal through the carnage.
What do you healers think?