I got in a little late: some of my friends bought N770s early on, but I didn't get in until the N800.
I own (still) an N800 and an N810. Though I haven't picked up either in a while, I thought they were nifty devices at the time, and should pick them back up again. I still think they have a lot going for them. (The N800 was actually the first mobile navigation system I ever used, with an external Bluetooth GPS and software based on OpenStreetMaps.)
I was unable to find an N900 anywhere when it was new. I was met with pretty much blank stares.
Eventually, an online vendor got some refurbished N900s in stock at a good price. I ordered one, got it, plugged it in overnight to charge...
...and in the morning, it was totally dead. I emailed the vendor and asked for an exchange because, you know, one bad one out of the bunch, they were refurbs anyway, no problem.
The vendor wrote back and told me that they had received a batch of 28 of them. ALL the ones they got had some sort of problem that resulted in a return, they would not be getting any more of them, and if I sent it back they'd give me a refund.
Thus ended my N900 experiment.