I'm having a similar problem. I was trying to create a webstore on this website www.jarafel.com. Problem is that Opera isn't displaying well. But Chrome works with no problems. I wish I could use Opera instead because it is faster than Chrome in my opinion.
I too have been developing a website, 100% zoom in new opera is way bigger than in any other browser including opera 12. I stopped testing in opera. What a waste of time