I’m thinking that’s a normal feature. The Bookmarklet area doesn’t just not render in Opera, if you look at the source code it’s not there at all. At a guess, I’d say that the WordPress code is programmed to do some browser sniffing, and if you’re on Opera it doesn’t serve the code to create the Press-It bookmarklet area of the “Write” screen.
In WP1.5 I remember that Press-It worked very well in Opera. I didn’t like how it worked in 2.0–rather than open a new tab where I could write the Press-It feature took over the active tab which really defeated the point.
With Opera’s tabbed browsing, though, I’m not sure you even need Press-It. It’s just convenient enough to open a new tab and go right to your WordPress dashboard and start up a post. And on Opera 9.2 when you open a new tab you’ve got the “Speed Dial” feature built in where you can pre-define up to nine webpages for quick access. My dashboard is number uno. 🙂