Sehmi is one of the last great non-AYCE Japanese restaurants in Mississauga and I believe they are doing well. You can tell by the odd hours they are open. I would recommend calling or checking out their website for hours they are open.
They have the usual assortment of sushi and cooked meals as well as some Korean dishes. The preparation and presentation are excellent. The interior is a little dated but the large booths are still wonderful for an intimate dinner.
The service is prompt and understated all at the same time. The waitress who I believe is the sushi chef's wife is kind however her English is not great, but who cares. She is patient with your requests to repeat what she said.
They have a good assortment of combo dishes, and the prices are very reasonable.