Battlefield is a very neat stage to fight on in Brawl. Aside from one personal problem I had with for the stage in animation, Battlefield is a fun stage to play on in Brawl.
Just like Lylat Cruise and Mario Circuit, you and your opponents do not have to worry about cheap gameplay elements getting in the way of combat in this stage. It's a stage where skill is put to the test which is a good thing for veteran players in the Smash Bros. series.
I know I promised to be unbiased as I can and care about gameplay more then animation and music in a stage but, I really should let it out about Battlefield that I do not like. (I am sorry guys if you do not like the write-up because of this.) I personally find the selectable music in Battlefield very "meh". Compared to the other simple stages in Brawl like Smashville and Final Destination that had very good music in them, I personally do not find Battlefield's music that good compared to some of the other stages in Brawl. I know there is some people out there that like the Battlefield music but, the music does not really fit my taste. One of the music tracks that happen in this stage is, the remix select character screen from Melee which, I personally do not like and IMO, does not fit the style of the stage well.
Aside from the music not being the best out there in Brawl, I found Battlefield to be a very fun stage to fight and play your opponents and friends in for Brawl. The animation is fairly well done with changing time zones from morning to evening that happen in this stage.
What counterbalances the music not being very good IMO, is how well the stage is well balanced. Anybody from young, veteran and newcomers gamers to the series can have an easy time fighting on Battlefield not having to worry about cheap gameplay elements getting in the way for the stage. Battlefield is one of those stages that simple and easy to pick up and play in.
Overall, Battlefield is a very fun and very solid stage to play on in Brawl.