I find on my Jazz, that while the Speed Limit sign reconigition works in most of the time, the road sign reconigition feature has only functioned once since I purchased the car in September.
99% of the time it picks up speed limit signs but the only other sign mine has picked up (over two cars in 4 years) is the no overtaking sign.
I find it to be an 80% useful feature. Sometimes I'm not sure what the current speed limit is and can check what sign the car last saw (as long as it wasn't too long ago). However, I've deducted 20% from the score because it sometimes gets confused, such as by reading a speed limit sign when driving past an exit to a roundabout.
I agree John. There are more and more 40 and 50 limits in my area and it is easy to lose track.
There are limitation to the system as John indicates. It is also susceptible to sunlight conditions.
If you are considering using it in conjunction with the intelligent speed limiter, you may like to search the forum as there are numerous points of view on that. But to summarise, it is an aid to driving and not a replacement. Ultimately it is your responsibility to drive within the law as any magistrate will be quick to tell you.