I've not come across a spinner program that writes readable articles consistently.
English is just too awkward for that a lot of the time. For instance, here in the UK we've got a town called Reading (but pronounced redding) - if a spinner program came across that town in an article as the first (capitalised) word in the sentence how would it know what to do with it. It's just way too complicated!
iWriter don't even let their novice writers work on reworded articles - you need to be above the base level writer.
Google "knows" the meaning of words in context and you can bet that it can spot a spun article a mile off. EzineArticles system knows plaigiarised articles when it encounters them and Google's budget is likely higher.