FWIW, and risking sounding like a broken record, my opinion on the topic of PIMs on the N800:

Nokia is first and foremost, a handset manufacturer to consumers. Yes, they do networks and have enterprise solutions, but to us consumers and many prosumers, they are a handset manufacturer

Therefore, I am of the opinion, that the Internet Tablets were designed primarily to be an internet companion to a mobile phone. If it wasn't for my Nokia E51, I would have the same concerns about the absence of a decent PIM. But the iT is not a PDA, and was never marketed as such (here's the broken record bit, sorry)

As a companion to a mobile phone for connectivity (with Wifi as a secondary, less ubiquitous means of connection), it does what my phone does not do well, i.e. open and read PDFs comfortably, browse the web with a desktop user experience, playback movies on a decently sized screen, Skype and other VoIP, etc.

For contact management, calendaring, and simple to-dos, stuff that I cannot do without, Nokia probably figured that users would more likely be caught without their iT than without a mobile phone. On a night out on the town with friends where I have no desire to tote around a largish device like the N800, I have all the important information that I need on my Nokia E51.

My E51 connects to my office Exchange server, providing me with push email, contacts, calendars, Active Directory lookups, and tasks. My contacts and calendar information is always up-to-date, and I never have to worry about losing data when I lose my phone, simply because all I would need to do would be to buy a new one and set up Exchange Activesync, and everything would practically be back the way it was.

My E51 also does double duty as a VoIP device since I have Gizmo set up, and with Windows Live Messenger, I keep in touch with my buddies over MSN Messenger, and with fring, I get to use SkypeOut (though it's rarely that good over HSDPA, but once I hit a WiFi hotspot, BINGO!

Sure, I could surf on my E51, but the user experience is nowhere close to what I get on the N800, and I certainly don't want to have to lug my notebook everywhere.

Plus, on a night out on the town, with all that's going on, I would so hate to lose my N800. So the N800 and all the enhanced functionality stays home, and my E51 with all the critcal functionality comes with me.

If I wanted a device that would work in WiFi areas only and not as a companion to the E51 (or any other smartphone, for that matter), I would have bought an iPod Touch which would have pretty much most of the functionality that I need, except that I would have to live with Apple's iTunes to get my movies over in MP4 format ONLY. Or I would get an eeePC, if I could be bothered to pick up Linux