Please post in this thread based upon your experiences with an N900. Also, please post the Version of the software, so we can honestly compare.
I'll start: Version: 2.2009.46-9
This is a prototype.
Things I love:
-Messaging (Conversations icon) This is seriously the best phone I have ever seen for messaging. I have used quite a few versions of Nokia symbian OS phones, a few Sony Ericsson phones, a couple of Samsung phones and an iphone. It is mostly the other software that enables messaging that make it great. The contacts application shows the different ways people are online, so it is one click to start an sms, skype, google talk, etc chat. All chats look the same regardless if it is sms, skype, google talk, etc. The multitasking allows you to keep many different chats open and switch between them quickly. I have left the chats open for a couple of days.
-Contacts. It's great to see the many ways you can contact someone. Call them, skype them, sms, google talk, etc. It's all integrated. What's also nice is the contacts application adds your google talk and skype contacts in the same list as your normal contacts, after you have entered your login credentials to skype and google talk. There is a contacts merge that lets you easily merge them all together. After that, you can scroll up and down to see who is online with different protocols.
-Media Player. Simple, fast easy to use. Absolutely add the Media Player widget to your desktop. One touch to start the music, go to the next or previous track, or to open the media player. I think this is easier than the iphone/itouch music player. (I am sure I will get flamed for that statement.)
-Ability to play the exact same video I would play on my laptop without use of any conversion tool.
-Image viewer thumbnails. These are fast and allow quick searching through a directory of images. If you select a directory from the file manager, it goes straight to the thumbnails, and is really fast.
-Speed of applications. The speed is almost the same as a PC.
-Many thoughtful little features, like the browser will go full screen after a few seconds. The N810 never did this, but it's a nice touch.
Things I thought was odd:
-Where the heck is skype? It is integrated in the phone and messaging applications. You set up skype, and can call people, and sms them, but it is not a separate application that you can start. After seeing how it is integrated, no one will ever need to start a separate skype application. D'oh! I just now saw on the Maemo select web page that it is "coming soon". Meh, it's already there.
-There are no more menus, just a screen of icons, and one icon says "More...". You select that to go to another screen of icons.

-The weakest thing about the N900 is how to find an application to start. It's just a screen of icons, but I know that many people will be asking, "Where's the phone?" Well, it's an application, and you can just click the icon on the desktop. On the iphone, they separate out the 4 most important icons at the bottom, so no one will miss them. Once the users get past this hurdle, they will be ok. Actually, the phone application is really good.

This phone is definitely for the under 30 crowd. Obviously I struck a nerve by saying this... Let me change that. This phone is definitely for the under 30 crowd and intelligent people. I have seen many middle aged people using the iphone, which requires almost no instructions, and they frequently seem to be asking for help. The N900 is quite easy to use, but will leave a lot of these people baffled. There is an initial learning curve that many people will not get over. It is definitely easier than any Symbian phone, though. How many people have asked you for help on really simple features of their phone, regardless of the model? I guess that's why they call them "Smart Phones", but they aren't talking about the phone... I'm in my mid forties, by the way....