For me it's a very simple question. I don't think there is another device that comes close to the N900 for me.

1. It takes breathtaking photos. Video could be better though. Just take a look at maximuscool's thread.
2. It has a wonderful hardware keyboard. No other device has this. I require tactile feedback. I hate on screen keyboards.
3. It has a resistive touch screen with pressure sensitivity. Multi touch would be nice..but I would miss the stylus a lot, especially for drawing. What other current device can use MyPaint like the N900?
4. It has some good potential. PSX and N64 are a stone throw away from being perfect. It has support for bluetooth controllers. Froyo is being developed for it. Meego may come to it. USB OTG should be coming. Browsing is great. I am posting from it right now. There is a workaround for flash with the chance of being ported from Harmattan in the future. And much more. So for me, the device is exciting.
5. Not to mention all the other hardware like FM Transmitter, Infrared, 32GB of storage + support for 16GB (possibly 32GB more), 3.5" screen with a great resolution.
6. The way most movies are supported just by copying them, and they look great. The kickstand may be small, but hey it's there.
7. It is a pure linux device, not running a virtual machine like android. Native linus applications can be used well and I have read stories of Linux Admins doing wonders with this phone.

I agree with this device replacing a desktop/laptop. This device is perfect in my opinion. The greatest disadvantage is Nokia's lack of support for the device. Sure it has its shortcomings, like lack of games but the pros greatly outclass the cons. At least for me.

This device is a pleasure to use. All the hacks and fun with it one can have...

So I'm sorry you were disappointed by it. I just can't understand how other devices will be better. This is only my opinion though.