Nokia now proposes a free service to Forum Nokia members: you can test your application on different Nokia devices through the internet, and it's called Remote Device Access.
The E90 isn't there yet, but it could be a good way to see how it behaves with different applications available before I possibly get one. The cool thing is that it's not an emulator, as the name implies. What you see is the display of a real device connected to Nokia's server. You reserve the device you want to test for a timeslot, and you can play with it. Here's a blog post describing how it works.