The only thing I can see wrong with using the title line, is people like me.
If I'm reading a thread, and I have a reply, most of the time my thoughts move faster than my hands, and I just end up clicking the "Quick Reply" button which, unfortunately, doesn't give you a title line.
So, I guess the search thread option would be the best... and I can't believe I've never used it before.
*feels like a n00b*