Since so many give feedback on what's wrong with FP, I will first say what's right with it.
Distance rendering is good, objects are smaller when they are further away. There is a reason why most assault rifles today have an effective range of about 150 - 200 meters without optical enchantments (most of up to 400 meters with optical enchantments). Actually if I am going to compare FP mode to any other game out there, it would probably be Operation Flashpoint. If you have played it, then you would notice that targets that are at distance are hard to spot and you must often look for moving shadows. Now of course because of the graphic details, in UC you have to look for small dots instead, but it doesn't change the fact that you may use realistic tactics like not walking on the horizon to remain hidden (how is AI detection in this matter anyway?). Well done!
Movement: Well done, have you been in the army SC? The breathing part with sniper rifle reminds me of my days when I tried shooting a high caliber rifle in standing position. The aim would always go sideways because both elbows are in the air. In crouch position the elbow has support, but your sight is going up and down because you are breathing. As for running and jumping around, it was relatively well done, not sure if marines equipped with gear that would weight over 20kg should be able to jump at all, but if improves gameplay for some people, then sure, why not? By the way, is the planet's gravity taken into account when jumping?
Weapons: Reload is ok, one thing that could be done is the ability to shoot that final bullet in the chamber while you reload in case of emergency. Not sure if I could justify hand grenades in an age where we have battlecruisers. Instead there could be grenade launchers mounted on weapons, but otherwise it's all good.
HUD: Maybe a different layout for widescreen users? Just a thought.
At last there is one small issue with the sniper rifles. When you zoom in, you have the same mouse sensitivity which makes it hard to aim (in situation like this i thank god for having a mouse with three different mouse speeds). Would it be possible to lower mouse speed as you zoom in?