Mirage make some great speakers that have limitations. I have found that the sweet spot is huge. Even if the speakers are close the the room boundaries the sound is very similar through the entire room. You do lose a little of the exact imaging though. I have listened to Martin Logans that had amazing imaging in the sweet spot, but if you moved, then the sound quickly degrades. With the Mirage's it is the opposite. You have much more trouble getting the perfect sound, but it is a very consistent sound.
That being said, the more breathing space you can give them, the better they sound. I have played with toe in and spacing and been very impressed with them. If you have a large enough space to give them a few feet of clearance, Omnipolars can sound amazing.
I chose Mirage because I liked the sound and wanted a speaker that could fill the entire space well. Once I moved them away from the walls a bit I was blown away by the sound.
I suggest you go listen to a set up. Walk around the room and see how you like the sound, and how the sound changes. If they let you, move the speakers tighter the corner and listen again. This will give you a better idea of the pros and cons of omnipolar speakers.