[CWuestefeld]

I have heard this claim. But in practice, with real Chinese people trying to read an unfamiliar character, I've never seen it actually work.

In English, we'd try to break out prefixes and suffixes, and come up with "some kind of disease", or "something to do with the heart". But in my experience watching Chinese people, unfamiliar characters just get a "dunno".

Could it be that the difference I'm seeing is because of the use of simplified characters rather than traditional? Maybe simplified characters have cleaned out some of the clues.

[pradocchia]

No, that's right. The best you can hope for is that you recognize the phonetic (typically the right or lower element of the graph), and match it to a word you already know from context. At best the radical is just a hint, a way to distinguish between multiple uses of the same phonetic character.

[cleaver]

One other thing is that the character gives no clue as to intonation. (EG. "ma" can be "mother", "horse", "to scold" or other meanings depending on the tone.)

[CWuestefeld]

That's OK. My voice gives no clue as to intonation, either. This is extraordinarily difficult for westerners to master (or to even hear at conversational tempo, in my opinion).