"Looking" sounds so much more proactive than "negative contact." Every time I hear some guy croak "negative contact" after a traffic call, it just sounds like he's given up and the controller should vector him around the traffic.
I do agree, and I use "looking" too.
The moment I hear ATC tell me the position I am "looking", and looking further once I hear the altitude of the traffic.
Just going OT here...
To tell an interesting story:
The other day I was taking off out of CDW (Caldwell, NJ) in our mechanic's flight school's Warrior to go pick up our 210 at N30 (Cherry Ridge, PA) where we had left it for maintenance.
Normally I would have called up NY approach for advisories, but they were too busy, and I knew not to bother him, so I just listened and kept my head on a swivel.
Prior to departure from CDW, I noted that my former Piper Dakota was out, and I was certain that one of my former partners in it had flown out to N30, where he is going for IFR training.
Sure enough, I heard him call in to NY approach, descending out of 5500', and the next thing I knew NY told him to squawk 1200. That was a surprise, but NY was so busy they wanted to get rid of him early.
Now, I knew he had TIS on his Garmin 430, but I had nothing of that sort on the Warrior, and I knew he was coming toward me. I mean, I am going to and he he coming from the same place, and we're both going "direct".
Knowing where I was, I decided to stay at 2500', knowing that he would probably still be above me when we "met", about 5 miles SE of SAX VOR.
Sure enough, I caught my former Dakota and friend passing off my right at about 500' above me and about 1/2 mile away a couple minutes later.
Sorry to get OT with this story.