It's similar in some respects to IGF but very different in many ways.
My (scattered) observations:
I was on the East Side, wayyy up, third from last row. @trueBlue83 sat behind me. We seemed pretty far away but it didn't impair our enjoyment. I've never sat that high at IGF but this seemed much further back. In fact, the entire upper deck was much further back. Seemed steeper too. IGF is feels more intimate overall.
The rows go down super close to the field at Mosaic. Much lower than IGF. I would hate to sit in the front row because you wouldn't be able to see much.
It was definitely quieter at Mosaic. Partly due to the cold weather (and having mitts on their hands) and partly, it seemed as though they were distracted. The crowd barely reacted to plays. Not sure why. Also, I didn't have many people behind me, so maybe it just seemed quieter.
Just like IGF, the East Side sucks - it was filled with Rider fans.
We were sheltered from the wind and covered, so stayed very comfortable all game. We dressed very warmly and had unzip our jackets a few times to cool down a bit.
They seats were really narrow and seemed cheap. I was thankful, with all my warm gear on, that no one was sitting next to me or I would have felt way to squished.
The screen at the south end is very large and clear. From our seats, we couldn't clearly see the screen in the north east corner. No biggie.
Didn't really care for their announcer. He seemed bored.
Their ramp to the upper levels was narrow. Honestly, I felt cramped because I'm used to IGF, but it's probably better that way. It would have cost them less and allowed for more room within the stadium.
No on field shenanigans. They kept all their promotions in the stands. Not sure it matters, just an observation.
The concourse on the upper East side was nice and wide. Lots of more room to move around. Also, when the sun was up, it made it seem much lighter up there. IGF seems really dark, day or night. But, a fan said to me when I made that observation, that it also created a big wind tunnel. The service was FARRRR better there. Much quicker and didn't seem confused with every order I made. I also observed that the staff were much older too.
The concourses on the lower level were sheltered from the field, as has been mentioned lots, so you wouldn't be able to see the game from there. Hence, more people in seats. I prefer the social elements of IGF.
Where IGF has all sorts of booths and stands that jet into the upper concourses, they have everything recessed. That makes things easier to move around but they didn't have tables to eat at. I'll take the Mosaic layout and space over the cramped feeling of IGF.
They have a good beer menu. Tall boy Heinekens were on $10. They had Blue Moon beer advertised at $9/can but I paid $8. I don't remember much else, sorry.
One bathroom on the upper East Side. Seemed really big but the line was slow at halftime. I prefer having multiple at IGF. But just like IGF, you have to constantly tell people that there are more toilets around the corner.
Bus system is less efficient than IGF now. With the corridor, IGF has them beat. But, I would say their system is better than what we had before the corridor opened.
They probably didn't love our "And that is another Winnipeg...First Down!" chant. But hey, it's was a fun way for us to connect with the other Bomber fans there. Again, though, I noticed how quiet their crowd was.
Most importantly, the crowd was very friendly and fun. We had a great time and won't hesitate to go back. Tried really hard to be respectful. One or two fans tried to goad us but we just played it super friendly.
EDIT: Forgot to add... Their scoreboard does not show team stats during the game. I found that annoying. IGF is not entirely reliable but it does update. Nothing at Mosaic and I missed it. I didn't want to pull out my phone to check the stats all the time.