Probably not that much, at least when comparing to French or English orthographies. Those two are very complex, and it's easy to forget about it because we used them for decades. But try teaching reading, then writing a beginner in those languages and you'll see for yourself how complex they actually are. Also communication with less educated people (in my company internal docs and code are riddled with mistakes in both languages) is revealing in that matter. I myself have to check very often if a letter is doubled or not, if a 'e' or 'a' is used in word like dependent and it doesn't help that cognates existing in French and English are often written slightly differently, which adds to the possible confusion.