There are many bikes to choose from in this (flat bar road bike) category. The Trek FX series is a very nice line of bikes, as are the Specialized Sirrus, Fuji Absolute and Jamis Coda Sport. I recently chose the latter, but the Fuji was a close second...and I liked the FX 7.3 as well. (I couldn't find a Sirrus at the time, but have been very happy with Specialized bikes in the past.) Of course, there are others. I've heard good things about Marin, Giant and Masi.

Try lots of bikes and wait for one that makes you feel like you are 'home' when you ride it. If you are planning to do half centuries, I think the flat bar road bike might be a better choice overall. However, there are many people who do the same with hybrid/full suspension models. I found the suspension fork and seat a bit annoying after a while-but that doesn't mean it won't work for you. As for the bar, I am in my mid-50s and do not find it intimidating at all. As long as the bike is a good fit for you, it should not be an issue.