OK,

i have the same problems.
After having owned almost all Nokia communicators, my trusted Nokia E90 was getting a little bit old, so in December I was one of the first in the Netherlands to get the N900, which I considered an upgrade from the old Symbian S60v3.
And I have tried to use the N900 as a phone, but it sucks. As an internet tablet or mobile computers its wonderful. Browsing with microB is fast (still better than Fennec). The RSS reader works very well. `Much better than on any of my previous owned smartphones/PDA. The camera is also great, much better and sharper and clearer picture than any of my previous devices. Messaging is great (although MMS is not officially supported). And there are great developers out there who produce or port great applications.

The problem is that I have to able to use my phone. As a doctor I am often on call, and have to be able to answer my phone, but there's the problem (as previously described in this thread). Usually when the phone rings:
1. the screen stays blank, so I can't pick up the phone
2. the phone application shows up, but the pick up button is not responding.
3. see number 2, but after a while it does, but sometimes too late.
4. sometimes it just works, but only in a minority of cases!

Nokia What about a hardware call button! Would that fix my problem???

So this is quite annoying. So I tried several things, like overclocking my device, which didn't help for the phone part, and occasionally filming stuttered, everything else was lightning fast.

I just can't trust my N900 for being on call, so at this moment when I am on call, I use the N900 as an internet tablet (like the old days) and my E90 as my SmartPHONE...
And I am waiting what Nokia, Intel or perhaps Android will bring with communicator style devices.