Are borescopes useful for inspecting cylinders?

[tashirosgt]

Are borescopes useful for inspecting cylinders on an engine that has been in use for, say, two years? Or is there usually too much soot to see anything useful? If you thread the scope though the spark plug hole, can you get it to make a U-turn and look at the valves?

[MyFreeCamry]

Borescopes are useful, but over expensive for average use. As far as making a u-turn to see the valves, don't see it happening.