I was finally able to test Sibelius 7 and I have to agree with the above poster about the ribbon, I think it is an improvement. Specially in the house, my family members have experience with MS Office and this helped them work in Sibelius, including the youngsters. I think that was a smart move by Avid, making Sibelius close to MS Office, they linked its learning curve to the learning curve of an ubiquitous software. I'm also having a good time with the new publishing options, I believe a lot of work I had to do in InDesign I will be able to do in Sibelius itself.
But, I'm really frustrated with the lack of improvement in the Playback Configurations. It's still the same, I think it has been this way since Sibelius 5 (or 4?). I can't make myself sit down and go through all the hassle of building soundsets, setting up the percussion, etc. At least here at VSL, we have soundsets provided, but for other libraries it is a mess. I think I'm going back to just sending MIDI data with text.
Oh, and finally true MusicXML support!