XE-1 vs Canon T2i (550D)
I think you really need to try the EVF. I was very cautious, and spent 15 minutes in a camera shop with the X-E1 before deciding. I've not used the 550D, but have used many many Canon DSLRs, crop and FF. The apparent size will be about the same as on the 550D. The image will have a slight lag - and a worse refresh rate in very poor light. Colours under artificial light may be a little strange. But when you half press the shutter to focus, the lens then will stop down, so you'll see what things will be in and out of focus, which you can't so easily on a OVF, without getting a very dim image.
Do try to get access to one; only you can decide. For me, it's fine; the advantages outweigh the disadvantages.