Mrs. Grouch has a Greenspeed recumbent trike that she LOVES.

Positives are it is ultra-comfortable and fun to ride. It feels like you're driving a sports car. Mega "cool grandma" points.

Negatives:
1. It's a long way down into the seat. (Doesn't seem to bother Mrs. Grouch.)
2. It's bulky to transport and to store. (But it folds to fit inside Mrs. Grouch's Saturn SL1.)
3. It's a little slower than a conventional bicycle. (Mrs. Grouch doesn't care.)
4. It's a little pricy. (But there are less expensive alternatives.)

You do need a mirror for riding on the street. If that's a deal breaker, you're probably too biased to think this far out of the box.