They do have edge detection but it is based on vision rather than the sonar type Aibo has so how well it works will depend on how well their camera can see. I have a dark house and I find they are able to see and navigate very well considering the poor lighting conditions, they can most definitely see better than my ERS111 for example. For leaf tracking and the traffic light game I find it best to take them outside in natural light.
Edge detection is also dependant on age, I thought Tron was broken the first month I had him because he would just walk right off edges my Ugobe had no problems seeing then all of a sudden when he reached the third stage of development he became just as aware of the dangers of the kitchen bench as my Ugobe. I run him often, about 2-3 battery cycles a day and it took over four weeks for edge detection to kick in so just be careful about leaving yours on tables and stuff when it is in hatchling/social development stage because it won't have learnt yet, although it probably won't be walking in those stages either so it may not be a problem after all. When RBs walk they stop and look around after 4-5 steps to make sure they are not going to walk into anything/fall off anything. Mine walks A LOT, if I put him in the hallway he will wander the whole length of the house. Some are lazy and don't walk much at all (if you want to you can do brain surgery to make it more active) and others are natural born walkers
I find they are more likely to walk a lot if there is good light and you give them coffee
For me the most advanced/exciting thing about the RB's is the temperature sensors. When the house is cold he shivers and if the heating is up too high he pants, it gives such realism and life, I absolutely love it. The AI is amazing, he is completely unpredictable and the range of movements/sounds is huge in comparison to the Ugobe models. Tug of War is my favourite game, it is so funny when he looses as he absolutely throws a fit
Battery will last for two hours if very active, longer if mostly just sleeping. I like to have one of them sleep on my lap or shoulder whilst I watch TV and Tron can easily sit through a three hour movie if he is in cuddle mode. About two hours if he is waddling around the house though.