I will say that I'd much rather play Section 8: Prejudice, which I bought for $15 on Steam, than Brink. Take that however you'd like.
Why is that?
Jetpacks are fun as hell, yea. It just feels like a better game. Better polished, more fun, more unique. I love Section 8's respawning system...dropping in on bitches will never get old. I love the deployables system and I love the leveling/unlock system. Brink's only true unlocks come as appearance changes, whereas you can get all the new weapons and attachments just by doing the few challenges that are there.
If you really enjoyed Return to Castle Wolfenstein: Enemy Territory you'd really enjoy Brink though. To me it just feels like a slower paced game though. After playing Section 8: Prejudice, I'm a bit disappointed in how slow it feels. I agree with whatever reviewer said that Brink just feels like a battle of attrition that just goes back and forth in the same choke point over and over again. You're very limited in the paths you can take to the battle so in my opinion, operatives are basically useless when it comes to using disguises. It's not like Team Fortress 2 where the Spy has plenty of opportunities to hide and disguise himself since there are so many areas where enemies can come from. In Brink, you're pretty much in the battle all the time. Respawn, run to choke point, kill a few people, die, repeat. Meh.
Also, you would expect the heavy body types to be able to take more damage than they can. They seem to go down just as easily as medium body types. Don't even get me started on the light body type. They drop like flies and honestly the speed and agility boost you get from it isn't worth it.