I've sat in the upper deck for many Brewers games in the past and trust me, it's a completely different experience than sitting behind the dugout or near home plate. Sitting on the first level and then sitting in the upper deck is bad because you've already been spoiled with decent seats.
I had a buddy who has season tickets in 428, so I get the occasional invite to a game. It's not bad, at least I don't have to pay for them because believe me, I wouldn't. I'm always able to follow the baseball and it's location. The tempo of the game will seem much slower on the top level than it does on the bottom level. The scoreboard helps greatly with your ability to keep up with the game but it could be bigger.

I also love how the sunlight shines thru the ballpark when the roof is closed on cold afternoons/evenings. The upper deck, by the way, is an awesome place to be when the team decides to close the roof to shield inclement weather. You'll attend a lot of Brewers games in person before you actually see it happen.