My 3 years old son loves it - you know, all those machines. Story are simplistic - sure, but that's all we need, really. I watch it too - I appreciate the subtitles and the whole concept too. Bob builds this and that, you learn a lot of new words, they are collecting waste and recycling, all quite practical for everyday life and really not that easy to find out in dictionaries the way you need it. The way normal people use it. That's why I like Bob, for the same reason I love Spot the dog. Thomas the tank engine is also fun with a lot of language, but its scope is a bit more limited. Spot and Bob are more "everyday life"-ish.
Quality is OK, no annoying unskippable commercials (like on Thomas' Hero of the rails, what a shame) + those subtitles, perfect bonus for me.