One of the big barriers at present is the lack of proper support for paid apps on the N900. The OVI store isn't working properly yet (big slaps) and also the device itself isn't locked down as tight as the fruitphone. Both these factors along with a smaller userbase means that the platform is less attractive to developers.

What type of applications are you looking for though? Maybe you could ask for a few and see what happens? revdKathy has suggested a couple and HopBeat seems to be the lad to make things happen quickly too.