The G1 had a famously small app space of just 70 Megs, and early indications are that the N900's space might be 256 Megs. It's taken me wading through a handful of Motorola Droid reviews to finally find out how much of the Droid's storage is reserved for apps.
The New York Times review of the Droid has it: 560 Megs. Smartphones are supposed to hook consumers with an always-internet-connected experience. "App phones" as David Pogue calls this class of phone add in often-paid small applications that add functionality and make the experience even more compelling. Do you really want the space they can store these things in to be limited?
In the end it really depends on how large these apps are on the phone, and whether for those apps that have large reference-style data sets those data sets can be loaded onto the external storage micro SD card or not.
From David Pogue's review, which coins the new term "app phone":
Quote:
Since Verizon seems to want a Droid-iPhone faceoff, here it is: the Droid wins on phone network, customizability, GPS navigation, speaker, physical keyboard, removable battery and openness (free operating system, mostly uncensored app store). The iPhone wins on simplicity, refinement, thinness, design, Web browsing, music/video synching with your computer, accessory ecosystem and quality/quantity of the app store.
I still like what I've seen of the Droid, but I haven't put my hands on one yet to know how much I might like using one.