The I is emphatic. The aorist tense points back to the mission of the disciples as involved in their original call.
Other men
Jesus himself and all who had prepared the way for Him, such as John the Baptist.
Labored (κεκοπιάκασι)
The perfect tense. Rev., rightly, have labored, their labor showing its effects in the present case. On the word labor, see on Luk 5:5. Compare Jos 24:13.