I switched to bents back when I was 55. Now I'm 60. I commute 18 miles round trip everyday. Last year I broke my femur and as a result have lost a lot of power in the leg. I added an electric power assist, and I'm right back up and running even better than before.
Some bents are lower than others. If this is a concern, choose one that has a higher seat. Most of them put you at the same eye level as a motorist. I've never found "visibility" to be a problem, in fact they give you a wider berth, just because of the "weird" perception they have of a recumbent bike on the road. Hills are different. You can't stand up, so you just spin in a lower gear. Since you can't stand up, you can put a lot more pressure on the knees, so care must be taken at first not to use too high a gear to go uphill. With the right rider, a bent can be a very fast vehicle. All human powered land speed records are held by recumbent bikes.