Blackpool midfielder David Vaughan joined the Black Cats on a free transfer on Friday following the earlier arrivals of Ahmed Elmohamady, Connor Wickham, Craig Gardner, Ji Dong-won, Keiren Westwood, Sebastian Larsson, Wes Brown and John O'Shea.
Bruce says he could hardly be more pleased with Sunderland's acquisitions ahead of the new season.
He told the club's official website: "The balance of the squad looks very healthy.
"We lost six players from the squad and we knew we were going to have to be busy in the transfer market. To bring in nine players is unbelievable when you see what most other teams have done.
"I'm delighted with what we have done during the summer. The phone has been hot and the transfers we have got over the line are terrific."
The fact that Bruce has made such an impact so early means the new arrivals will get a full pre-season under their belts on Wearside, and that too is a source of satisfaction for the manager.
He said: "We have added the players now, so we can work with them all throughout pre-season.
"I'm very pleased with what we have done. There have been no other clubs as busy as us and I'm looking forward to the season starting."