While still hot & fresh from the oven, here you will find out about Maemo 5 (Linux platform) in Nokia N900 Rover. From their website, it seems that Maemo 5 will only be allocated for high end Nokia series & high-end smartphone with has fast processor in operation & also the internet access.

Video: NokiaConversations

Some features that might be interesting in Maemo 5:

Browser
Maemo Browser promised a browser that uses Mozilla technology with rich features & of course it has fast web page load that similar to the Mozilla browser. Maemo Browser also able to play video with high quality video & animation that supported by Adoba Flash 9.4.

Multitasking
Just like Windows Mobile, Maemo 5 also able to do multitasking, which means you can open several types of applications at the same time.

Contacts
The existing address book (phone book) was able to integrate with a variety of web communication such as Ovi, Gtalk, Skype and others. With this feature you can open all the necessary contact data from telephone, email & web.

Additional Applications
Well, this one might take time but in the future it will grow up, because Maemo 5 is open source. But for now, it is very difficult to find applications that can be used in Maemo 5.

Other
Actually there are many, but for other features, it is similar with Windows Mobile such as Copy & Paste functionality between applications.