First, I want to say that I had read quite a few threads here, like N900 vs Nexus One, or N900 vs Milestone/Droid, but I am still confused.

Please excuse me for opening a new thread with a similar title again. But I think it will be helpful to people with the same question if we have some discussion on this.

Please let me say something about myself first. Recently, I am using Nokia 5310 Xpress Music, with the Symbian OS. Not a smart phone, even not 3G network, so it is a big upgrade.

And on my PC, I installed Windows XP / Windows Vista / Windows 7 / Ubuntu 8.04, you know, kinda like a geek.

The problem is that I can only afford one device. So I want to choose the device that most suitable.

After some study, I find that :

Nexus One has quicker CPU and larger RAM, but with no QWENTY keyboard. The camera and speaker also not perfect.

Milestone/Droid has QWENTY keyboard, but the CPU is not so quick.

Both the above device use Android 2.0/2.1.

N900 has QWENTY keyboard, a bit thicker. But with a different OS, the Maemo. And recently, N900 had been found that can be overclocked.

It seems Meego can run on N900 and it is an exciting news.

But Firefox had release a web browser for Android (Fennec), so MicroB has no more advantage now.

I have several questions now :

1. I was told that the Android OS is based on Dalvik virtual machine and most apps are based on Java. So Android is not a true Linux, is that right ?

2. Somebody say that Android or iPhone OS had limited access to the root, but I find Terminal on both OS.
So is it true ? Because now I runs Ubuntu on my PC and I like the feelings that keying the commands in the Terminal, write some shell scripts, do some configuration, etc.

3. Another problem is that Android has more apps, so is there any "killer apps" that can be a good reason to buy Android device ?

4. So could you give me some advice on which one to choose ?
Especially the people who have used both Maemo device(N900) and Android Devce(Nexus One / Milestone / Droid).

Thanks !