I finally got one sitting on my desk. I've still to install the one true editor.
First impressions are good. It is quite snappy for a 400Mhz ARM chip. Relative to the e61 things are quite nice. The storage quickly becomes an issue. Luckily I have an 8gb microsdhc card in it, so data files can be taken with me but still I would like to have more storage on the go... but many have noted the blow of only one minisd slot relative to the two full sdhc slots on the n800. Luckily the n810's microUSB seems to work with USB OTG stuff. This will be interesting with 16gb usb thumb drives, being able to plug in a card with a bunch of data on it.
I've already done the whole dual boot by reappropriating the internal 2gb card to be the new boot drive. The 256mb root filesystem might be great for users who don't want to treat the n810 as a little linux machine, but for the serious hacker having a /partition that is over 1.5Gb makes for a much more enjoyable system to install software on.
One very surprising thing is that stuff like kernel side encryption of partitions is so hard to do out of the box. Encrypting /home on a laptop is standard practice, but with an n810, much more stealable than a lappy one would really *need* to have the data become unaccessible to any would be thief. Sure you loose a cool piece of hardware, but allowing someone who has just stolen your mobile device access to your little digital world is just a no go. I would have hoped that you could just install an extra kernel package like for NFS to get device mapper and ecryptfs and luks working without much pain. There are precompiled kernels and modules for luks but having nokia offer a bunch of kernel modules in grouped "kernel-extra" debs by default wouldn't be that hard for them to do and would make the whole process much easier.
I still haven't managed to get FUSE going yet. I guess sadly that it might be true that folks don't care too much about funky filesystems while on the move. But that won't stop me forcing libferris onto the device. Mounting postgresql, sqlite and XML from the n810 isn't going to be any less fun than from the desktop ;)