[tvandyck7]

It really depends. An app like "Google Earth" is much larger than an app like say "Not Call Log". Of course 3D graphics in apps such as games like Doom(10mb) are going to take up more space. I'd say you'd have, at most, 3 or 4 of these on your phone and the rest will be performance enhancing smaller apps that take up a dismal amount of space. As far as how many.... I can't really say. I will say that it will hold more than you will ever actually use and still run perfectly fast.
And if you flash a rom such as Adamz or DroidMod, you can customize what is installed at the time of flashing and save a ton of space.
The phone has 256mb of storage space. I just checked my phone's available space and I still have 90mb left with everything on my phone! That's more than most WM phones bare bones.