I have seen Montreal from Whiteface as well.
Dont remember what I saw from Marcy ..we stayed about a nanosecond as a lightning storm roared in.
We often see 150 miles from the top of Washington with favorable (cold) atmospheric conditions. We can certainly see some of the eastern ADK peaks from the summit.
The Atlantic Ocean (70 miles by crow) is right at hand it seems
Here is a fun little blurb written by a summit intern about visibility looking IN to the Adirondacks from the outside.
http://www.mountwashington.org/weath...=2009&month=09