My main home machine remains my Mac. (Actually a MacBook Pro that mostly lives in a dock.)
But my Gemini has replaced my dumbphone, and my iPod Classic, and is well on its way to replacing my Psion 5mx. Which, considering how much I used those gadgets, especially the Psion, is saying a huge amount!
The two main things I still use my Psion for are its Agenda (I'm waiting to see whether Planet's app will be a suitable replacement), and as a reader for the CIX conferencing system (for which I co-wrote a dedicated application; there's a web front-end but it doesn't work so well on the small screen, and I'll probably have to write a new app for it, but that'll take months.)
And when I went on holiday a few weeks ago, I took neither my Mac nor my Psion -- the Gemini was my only gadget. I was very happy to be browsing the web (including this site!) while travelling down the motorway in a coach! It saw a lot of other usage, too.
But main machine? No. It's not up to editing video or encoding it with Handbrake, developing software using IntelliJ, recording music with Cubase and software synths, or many of the other things I use my Mac for. And without an HDMI cable, even web browsing and email is too painful to do much of on the small screen.
OTOH, my Gemini is always with me, and so it beats my Mac on several other scores!