Answer to both:

I don't see how I could handle hundreds of long, technical mails daily, many containing code patches to be acted on, using a mere Blackberry. Have you ever seen someone send you long, thought out mails containing good quoting and tested code, to a suitable quality for technical development lists followed by "sent from my BlackBerry"? Didn't think so.

Actually doing remote work, e.g. config or code fixes, or examining someone else's system to debug it (I do a lot of troubleshooting) is another important use. Not for long periods of time, but immediately on the spot when needed.

A good screen, custom software and remote shell are required. N900 or laptop are the realistic only options. It's nice to be able to do it without getting out the laptop sometimes. I do like doing consultancy work in nice cafés with a battery that lasts 36 hours

Now that the N900 is here and I've got used to using it, I plan to develop software to specifically help manage my personal workflow in other ways, even when the laptop is used alongside it. This sort of thing is not Blackberry or iPhone territory unless you get into being a devoted app developer. As I've noted, Android is getting closer. Right now the N900 is best for it, by far. Custom software is so easy, it's a no brainer to write personal-use-only apps whenever it's convenient. For personal scheduling, tracking and prioritising tasks and so on, it's a great form factor, and being able to link those directly into work that's being done (e.g. patch flow tracking, email tickets, issue trackers, phone call logs!) rather than side by side with a regular PDA, that something very promising.

Now when they fix the 3 SIM and MMS (or community may solve MMS), I'll have no need to carry the second phone because the N900 is quite good as a phone really, despite silly UI problems. Perfect