True, though definitely much less than there is in English. And the rule for "ha" as "wa" is fairly straightforward.

I think people do say "-desu," it's just that when you talk fast, the end "u" sound goes away. Sort of like how saying "could have" fast turns into "could of" turns into "coulda." I have heard people enunciate the final "su" for "desu," and it mostly seems to be in more formal situations. The end "-u" sound usually goes away for "-masu" as well, probably for the same reasons. I'm trying to think of words ending with "su," but can't. I suspect the "su" sounds more like "su" in the middle of words because you need the vowel to differentiate it from the next consonant sound.