What's really difficult about French for anglophones is not learning to read it (or understand standard spoken French, that gets rid of all the spelling difficulties). It's rather to express themselves that's far more difficult than say, becoming fluent in written and spoken Spanish (which is really is, both for French and English speakers, because the language is so straightforward). In speech, at least simple and casual conversation, it's not so bad. But I've rarely seen anglophones (other than professionals and other special cases, of course) who have not lived among French people and have practiced written French quite a lot who can write more than half-decent French, and the more subtle or precise what they're trying to say, the worse their French gets. In a large part, I think it's precisely the similarities between the two languages - and the many pitfalls the differences create - that make it so difficult (it's a bit the same for us but English is more forgiving), and that's due to the plethora of subtle and less subtle semantic shifts, and that requires a lot of time and constant contact with the language to master (of course, the French have the reverse problem with English words), and all the small differences between French and English syntax and grammar. Barbarisms and anglicisms await us at every turn (and the more you read and speak English, the worse it gets), be it French words we use in their English sense that doesn't exist or is improper in French, and more insidious, turns of phrase or expressions copied on English that are incorrect in French (and this is getting worse and worse in the "global village" as Québécois and French alike more often read and write in English nowadays (even natives have specialized reference books to spot or verify all those). It used to affect mostly Canadians and mostly people who spoke both langagues (and worse in Canada outside Québec), but the problem is becoming quite widespread too with the younger European francophones. Anglicisms are often to blame for confusion between European and Québécois - they don't understand what we mean because we give a word a meaning it doesn't have in French, or we use a turn of phrase that mimic English.

For anglophones who were not academically educated in French - learning the syntax and grammar the way native French speakers do and not as a second language, it's the same except much worse - and something hard to improve on (unless you not only read a lot of well-written material on a frequent basis but also write a lot, and get corrected by native speakers who master their own language well enough to spot your semantic and grammatical mistakes). Often enough, we understand what these anglos wrote not because it makes much sense in French, but because we have enough English to puzzle out what they really meant. As I said, the reverse is a bit easier, as many words in English have a much wider acceptable semantic range. Self-taught people like Larry and Tom probably face that problem very often. For the larger semantic shifts, the sentence won't seem to make sense and will drive them to a dictionary, but for most of the more subtle shifts (eg: when words have roughly the same meaning, but carry different connotations - the word "distinct" for instance) they most likely don't even notice them. I see that all the time with bilingual anglophones around me. They do tell us from time to time a word doesn't mean what we think it means in English, but it's far more frequent we have to correct their usage of words in French, or put them straight because they've taken a word in its English sense and thus misundertstood the real meaning, or the implied connotations, of what they read.

There's not a lot of those. Give or take a few regionalisms or accents, there's barely any difference in the French spoken through Québec, especially since the spread of mass media. The regional differences are more marked in France. For the French, Montrealers arethe worst, because we use even more anglicisms. But it's not as bad as 50 years ago (when the French would have had problems understanding a working class, not very educated Montrealer), as knowledge of English is far more common in France nowadays.