All Serbs claim it's a dialect of Serbian and all Bulgarians claim it's a dialect of Bulgarian...

Serbian and Bulgarian linguists have been fighting over the issue, and especially before WW2 it did have some pretty heavy political implications: The way of thinking was that if the Macedonians were really speaking Serbian, than they should be a part of Serbia, and if they were speaking Bulgarian, they should be a part of Bulgaria (Greek scientists also entered the fray and claimed, based on folklore studies, that the Macedonians were slavified Greeks, with the same political implications). Thus, this is a mine field! (Just a word of warning.)