[FlyChicaga]

Here is a major problem I have with the "We've got 'em on TCAS" call. Many pilots out there seem to have this bad habit of stepping on one anothers radio calls, usually when they are handed a frequency change. Instead of waiting a few seconds to see if anyone is talking, they switch and immediately check-in as if they are the only ones using the frequency today. That can cause this:

ATC: "Traffic to follow 1 o'clock, five miles, A320."
Pilot: "Roger, we've got 'em on*squeeeeeeeeallll*in' in at 5000 with Whiskey."
ATC: "Roger Airline 1234, maintain visual separation with traffic ahead, you are cleared for the visual approach to runway 10L. Contact tower 123.45."

See the problem now? You don't really have them in sight, but you are now instructed to follow them utilizing a very basic instrument. TCAS is useful, but I'd say more in how it keeps you from colliding with it's internal logic, not in the visual display it provides.

For traffic calls from ATC, I now have two replies only: Traffic in sight, or looking for traffic. I want ATC to know I have the aircraft in sight, or that I acknowledge their advisory and am taking a look out the window. Even if in IMC, I'll just state "looking for traffic." The call "in IMC" does nothing for the controller from what I've been told.

I have a good article on my computer (wish I could post it) about TCAS troubles when pilots do not comply with ATC instructions due to what they see on the TCAS display. It has caused a few near misses because the pilots did not have the "big picture" and considered ATC was vectoring them into other traffic without a visual on them.