I'm very tempted to get a robomower (RL-800), but I'm not sure it's
really practical. My main concerns are the narrow areas of my lawn
that may require manual mowing, and sidewalks.

If I have to drive it manually over a 50 X 5 foot area, will it be
agonizingly slow?. This area is also sloped. Is it difficult to stay
on course when mowing across a slope?

I have a corner lot with lots of street frontage and sidewalks.
Unless I include the sidewalks in the mowed area, I will have to
create several very small zones, consisting of the area between the
sidewalk and the curb. This would seem to largely defeat the purpose
of having a robomower, since I would have to attend to it every 10
minutes to change zones. Would it be unsafe to have one large zone
that includes the sidewalk(s)? If I have to split it into smaller
zones, some will only be about 6.5 feet wide. I read somewhere that
the mower must be started at least 4 feet from the perimeter wire, so
I may have to mow those areas manually. Is that true?

One final concern is curbs. Does the mower follow the wire
consistently enough to mow over the edge of the lawn without falling
off the curb? The curb is only about 3 inches wide.