Well, I have both N8 & N900.

I prefer using the N900 for texting, internet access and day-to-day use because of the hardware keyboard.. The N8 lacks this- and I personally love the N900's keyboard too much..

N8 is great.. It has a great camera, nice apps/games and 'proper' support from Nokia (well until now anyways).. The OS is still 'old', but apparantly new UI and features are on the way... but as I said, the N900 has a keyboard, a better OS (more powerful...) and a community which you can always refer too...

I use my N8 as a second phone- mainly for taking pictures, OVI maps and games, but the N900 is my real phone/mobile computer.