From what I understand, the Korean written language was pretty much invented wholesale by one man (the king at the time, I believe). As such it's a lot better designed and internally consistent then other written languages (which accumulated naturally over time).
That said, while it may be easier to learn, I imagine people still read it at about the same speed they would read English or Chinese. I don't remember where but a while back I read an article saying that basically all spoken languages impart information at roughly the same rate (e.g. languages with higher information density are spoken slower, languages with lower information density are spoken faster). And from the OP's article it sounds like this applies to written languages as well.
That said, while it may be easier to learn, I imagine people still read it at about the same speed they would read English or Chinese. I don't remember where but a while back I read an article saying that basically all spoken languages impart information at roughly the same rate (e.g. languages with higher information density are spoken slower, languages with lower information density are spoken faster). And from the OP's article it sounds like this applies to written languages as well.