It's not all that spectacular. It's just your standard FPS with an RPG twist.
All the fights are basically UT2k4 deathmatches with up to 16 or 32 players depending on your location. In the "Battlegrounds" you can have up to 16 vs. 16 while skirmishes are 8 vs. 8. I don't know where game magazines are getting this idea that you can have 64 vs. 64 and 120 vs. 120 sort of conflicts... I've been looking all over for this conflict zone, but I haven't come across it. Maybe it hasn't been implemented yet. I think since they're planning for a console launch later that they may be holding back some of the features on the PC version.
As for the classes, there are some massive balancing issues. I ran through some of the most difficult areas on the avenger class - medium range ~ 30 feet - and cleared them out solo, whereas while playing on an enforcer you need help, and lots of it.
As far as the PvE teamwork goes, I'm yet to experience it. They seem to be using Peer-to-Peer ports for everything (instances, towns, deathmatches, etc.), and this creates a serious lag for most players. I really haven't noticed the lag, but then again it could just be that my machine can handle all the on-screen graphics. Though there is one thing that I did have an issue with regarding the P2P system... the couple times that I tried connecting to "Squad" based instance, I gave up because it took 5+ minutes to connect (one time I let it sit for 30 minutes).
The RPG elements come in with unlocking new perks more or less. Similar to in other FPS games, you can unlock new stats as you level up, such as add-on slots for weapons and gear or increase your capabilities in weapons (C Rank to B Rank). You then need to turn around and buy your individual perks. The new weapons and armor provide extra protection and/or damage, but its really not that spectacular... you're counting minimal points of added damage like from 114 damage to 119 damage.
I'm not sure what'll be in the cash shop, but you can probably assume lots and lots of costume garments and XP bonuses.
I may decide to pick it up post-launch, but I'll hold out for the rest of the beta testing to make up my mind. Right now, despite the fact that I haven't really enjoyed it, this is probably the best F2P MMOFPS available.