I just flew SXF-DUB-SXF this past weekend. Both flights were pretty full-- if not 100%.

I traveled in economy with my TravelPro (http://www.luggagepros.com/travelpro...llaboard.shtml) and a standard size backpack. The TravelPro was not overstuffed, and at Berlin (SXF), nobody said a thing about my bags. I fit in the overhead of the A320 (as it always does!) and had no problem putting the backpack under the seat in front of me.

On the return from DUB, they were walking around the gate area asking people to put their bags into the bag sizer. Mine fit no problem, and I was allowed to bring it on board. But a couple people with larger bags had to check them and they were tagged and put in the hold, free of charge.

Hope this helps!