Summary executions by officers that don't leave them open to prosecution because it's part of their job. Dissension among their higher ranks over decisions that both demonstrate strength and weakness in equal order, leaving other races guessing as to what is really going on. They are also on the lookout for uninhabited planets for colonies of their own people to take up residence. The galaxy has suddenly become a much smaller place. Worse, your part of the cake has suddenly got extremely small.
Resistance is futile.
You are not entitled to their technology unless your own scientists have already designed and have working similar machines themselves. You are basically left in a backwater knowing that there are other races over head that you will never be able to compete with on an equal level. As you will never catch up, scientific development falters. There are no targets to aim for when it's already been done before. Radical scientific thought is lost.