Would you still go through the roof if Disney provided you an alternate, if lesser, form of transportation during the hours the boats were unavailable?
The primary purpose of this temporary change is for construction of the Grand Floridian DVC property - not maintenance. Sure, necessary maintenance will be done, but the MK monorail loop is being closed in case a multi-ton steel beam falls, or the crane topples, or something.
As for advance notice, check out this http://www.disboards.com/showpost.php?p=44259923&postcount=481 really informative thread on construction permits, timing, authorization by creativeamanda from a few pages back. It helps explain why there's often not a lot of advance notice TO give.
I absolutely would still go through the roof! Monorails and buses are not the same. Rip down the monorail and the prices of GF, Poly and CR rooms drop $50/night easy. That's a big piece of what people pay for. Same with the boats. When's the last time you heard a kid ooh and ahh and beg to ride a bus?!
They need to do what they need to do, but