* Google may see it as an attempt at optimization.
I've had mixed results.
For MOST of the pages that I have changed, I looked at the keywords that were being used to find the page, then changed the titles to better incorporate those keywords. (I also changed the H1 tags and meta descriptions, for what it is worth).
Result: A modest increase in traffic to those pages.
However, I haven't checked the rankings, and to be honest, I have NO IDEA what titles google is serving up to its users. Could be my new titles, could be the old titles, could be something else entirely.
There were a FEW where it seemed to go the opposite way, and I quickly returned to the original titles, and within a week, traffic was back to normal.