Having flown for 3 years with an operator having a mixed fleet of IAE and CFM engines, this is what I perceive as discernable difference between the IAE and CFM engines, in addition to what has been already elucidated in this thread.
1) IAE has higher thrust idle, hence as a pilot you'd have to apply brakes considerably more during taxi. Leads to frequent usage of brake fans to keep the brake temperatures under control. The difference is significantly noticeable when with the parking brakes on, you feel that the aircraft is constantly pushing against the brakes, causing a bobbing motion.
2)IAE has higher start time compared to CFM due to the extended motoring to get rid of an unique problem called 'Bowed rotor condition'. And the idle time required before take off after a cold start is higher compared to CFM.
3) IAE is much more noisier compared to the CFM, though as a pilot I'd complain because, pun intended, I'm made more aware of the thrust changes without having to look down at the gauges.
4) IAE gives you a remarkably lower fuel consumption compared to CFM engines.
5) The target speed achieving characteristic of the ATHR on the IAE engines was inferior to the CFM ones, though I've my suspicions that it's the software standard of the specific ATHR that makes it look that bad.