Maemo is pretty important for Nokia. Nokia has simply nothing comparable to Iphone/Android. If Maemo doesnt rock - Nokia will have a problem!
Hopefully Nokia can deliver the phone soon. As for me its critical to have something soon. And I think there are a lot of Nokia Users having some E Series or N Series phones awaiting something to replace their old gadgets but were disappointed by the N97 (as I). If Nokia can bring these users to there N900 there will be a critical mass of users that will make maemo attractive for developers.
In my opinion linux users that use linux because of its openess and possibilities will come to maemo sooner or later.
The question is how to attract dissappointed IPhonees and Androidees? Its all about the weaknesses of others Phone OSs as the convinced ones will not have a reason to come to N900/maemo as they spent a lot for a new phone in the last two years.