I got a new N900 yesterday. I like it.
I didn't, however, like the browser. The inability to open new taps was the killer for me, for all its rendering speed.
I used Opera Mini on my 5800, and was pleased that it did tabbed browsing, but it just wasn't that good for form filling. I get a lot of trains, and cannot always be sure of my connections before setting off, so a phone that allows me to search for onwards trains as I'm nearing a stop is what I need. Opera mini did not allow that. With all their stuff being pre-rendered, it was fast, but hitting up thetrainline.com or scotrail.co.uk was useless, as once I'd filled in a form I was unlikely to get any meaningful result.
So I've been using firefox 1.1 since yesterday, and its everything I need. Not blisteringly fast, but it is intuitive, tabbed, and compatible with modern websites with javascript et al. The only challenge was finding out how to make it my default browser, but, as they say in apple parlance, "there's an app for that", so it was righted in short order.
Also, while opera mini looked good on the 5800, on the N900 it looks terrible - the border menus are ungainly and look poor.