Well.. I was just like you.
A hard decision between satio and N900. Based on this conversation, I've chose N900.
Well, you probably already got your phone, but I'll post here my experience to help other people that stil didn't.
I don't know Satio in deep, as I just played a little bit with one on a phone store. So I don't really know if I made the right choice, but here it goes what I *really* hated about n900:

- Its very, very heavy! It wants to be remembered it's on your pocket every minute! Its also quite thick. I think I would get used with it, but I still don't.

- There is no "portrait" mode. Everything needs to be done in a "landscape" mode. Because of this, you need to operate it with both hands. This becomes very unhandy on everyday usage.

- Media player (a must-have for me, specially for audio)
1. Don't have an equalizer. You read it right. You paid $400~500 for a device that don't have a equalizer. (yes, I know there is a workaround with some dude's mp-renderer replace, but this dont work at all. your device gets freezy and even higher on cpu load)
2. There are no physical playback buttons. If you are walking with the phone in your pocket and you want to skip/ replay/ stop the playback, you need to take the device off, unlock it, wait it to become responsive and press "next". Its a fast 7 or 8 steps to skip a track. Oh yeah, you will need both hands!
If you're not using the official media player, the volume keys also don't work after phone gets locked.
3. The media player widget "play" button stops working. (Yes, I am on 1.2Pr firmware. It's still buggy.) It also takes about 3 or 4 seconds to open the media player app from the widget.
4. Depending on the codec, the video don't run smooth. (Thats no big deal for me, as I dont want to watch movies on a phone).
5. You notice that audio playback is a very heavy task for the N900 to deal. I don't know n900 hardware/maemo os in deep. I belive there is a "higher level" framework to deal with audio that punishes the cpu.

- FM radio is something special. Its an analog (radiowave receiver) to digital (digital audio) to analog (earphone). That makes the device laggy, battery eater and the audio still keeps freezing. Yeah, when you listen FM radio!
Plus, volume keys don't work for FM radio with device locked.
Also, the Fm application made by some guy is not well designed (It searches for every 1kHz step, when actually station frequencies are set 10k or 20k from each other. This makes the app to find "incorrect" frequencies for the radio stations. I'm not blaming the developer, as he made a favor for the comunity.


- It's laggy when you receive a call, or alarm, or some reminder.
You keep tapping "Answer!" "Answer!" "Answer!" and the phone is still ringing.
Also, if you are on that meeting and the phone starts to ring, with my old K800 I just press the volume button and it stops ringing while still waits for me to answer the call. This gives me time to identify who is calling me, and to think if I'm going to answer it or not.
With N900, It keeps ringing and ringing, while I'm desperately tapping "busy!" "busy!". Thats awful.

- The battery is a disaster. You are lucky if you get more than 24hours (no phone calls) with the phone still running. Don't come suggesting to turn the wireless off or disable 3G internet. If I would't use internet on this phone. I would keep my old K800!

- The camera (although I've seen comments over the internet saying the opposite) is not good, specially under low light conditions. I was expecting at least a more sensitive sensor. My old K800 still makes better photos.

- There aren't many basic functionality that you would find on a $50 phone.

The good apects are: Excelent display quality (impressive resolution), the OS is well designed and flexible. The integrated conversation (sms, messengers), and the voip are well done.
Also the web browser, that can do everything a computer browser can, in a small size.
Altought you get many open-source applications available, you won't find professional, mature applications for this phone.

The impression is that it's software is still pretty imature. (beta).
The lack of many well thinked details makes me not to like this phone as I think I would.

ps: I know my english sucks. I'm sorry about that. I hope the idea get transmitted.
Every 5 minutes I remember one more thing about N900 that pisses me off.. This list won't end up so soon...