Well, I think it's important to distinguish between 'tabloid astrology' and the more professional kind. I think it was Linda Goodman who wrote that these tabloid predictions had nothing at all to do with real astrology. I can't be sure, but I think that the 'real astrologers' today do not claim to be able to foretell the future.
Instead, they see the *vibrations* that the celestial alignments produce, and make educated guesses. For example the'prediction' that the age of Aquarius will be one of spiritual rebirth is more of a general description than a prophecy in my opinion.
And while it is true that Nostradamus was an astrologer, I don't think he used this to make his predictions. As far as I recall reading once, it was more a process like Remote Viewing. He would go into a trance like state, see visions of the future, and then when he 'came to' he would have several pages of notes written, which he then converted into prose form to avoid antagonizing the church at the time...
Oh, and not to bring up the whole free will debate again, but I think that I also read somewhere that Nostradamus did not believe the future to be written in stone
In fact, his prophecy that the 'King of Terror' would return in the year 1999 and 7 months certainly didn't come to pass.. unless I've missed something :P
Just my thoughts on the whole matter 