The biggest killer for me for the game though is that you have to play about 70% using the night vision goggles or you will not find the enemy. The fact that about 55% of the game is at night plus the fact that even during the day the shadows and lighting are so dark that you HAVE to use the goggles just about ruins the game for me. What that means is that most of the game has nothing more than green blobs for graphics. I find it to be a copout. Realistic? Probably, but just not that fun or interesting to stare at for 10 hours.
Personally, I turned up the game's brightness quite a bit to keep from using the goggles constantly, as it annoyed the crap out of me as described above.
It still was dark, but at least I could see more than 10 feet in front of me (without using the green glow of doom).
I'm afraid I don't understand where you're coming from on this problem.
I played the entire game through in 7 and a half hours (which is well short of the average playtime for most people, but I generally do really well with the Ghost Recon games of late) and had to use the thermal goggles maybe twice through the entire experience. Any other time I fired them up it was because I wanted to see through a smoke grenade cloud, or just wondered how effective they were in a given situation.
Are you, by chance, not playing on an HDTV? It could be that without the clarity one provides it might be more difficult to spot enemies. I haven't played the game on a regular TV though, so I'm honestly not overly sure.
As for the save system, I only had one negative encounter with it where I reached a save point after myself and two teammates took the biggest portion of a grenade blast and had almost zero health left. I spent about twenty minutes replaying the same small section because I kept catching a stray bullet here or there and dying. I finally went at it a good deal more cautiously than I had before and made it through to the next area.