So I've been enjoying the game and feel that I wanted to share/comment on a few things I've seen thus far.

To address the cover question, if the shields on your cover are red then it's no good or you'll be flanked, I haven't seen much beyond that yet to indicate flanking/LoS.

For the sniper debate I find Darn Good Ground (edited for forum filter), squad-sight and the spider suit to make a VERY nasty combo. In the terror missions I've run they've given me 100% hit chance with 50-60% crit chance against the opponents even fully across the map. My sniper with double tap is the reason that I was able to get the achievement for all excellents on my last mission.

I've found that run and gun is most useful as a means to get that last burst of speed to reach distant cover and still be able to overwatch/rapid fire if need be.

Cryssalids are really not as scary as they used to be. I had one mission where one of my assaults opened a door and activated 3 of them who cornered him. Killed one with rapid fire and hurt the other two with other shooting but didn't kill them, I was afraid that I was going to be down two guys with zombies in my face to make everything worse but found that two guys just took 9 damage hits and breathed a HUGE sigh of relief.

Overwatch is AWESOME for escort missions, by using it effectively and keeping my squad spread out I've been able to keep the enemy infiltrators from being able to attack/move at all on my returns. Nothing is quite as ridiculous as watching 4 people all overwatch the same thin man as soon as it jumps onto the overpass.

ARMOR IS KING!! Learn it, live it, love it. The casualties I've had were from when I ran soldiers without it and they ate rather unfortunate plasma rifle fire. Carapace is a good baseline but certain classes benefit from the abilities in variant armors. I really like the skull/spider suit (can't remember exact name right now) for my sniper for the extra mobility/grapple option and a friend of mine uses it with his supports for the extra movement to get to wounded soldiers more quickly. I've just finished research on the Titan and Ghost suits and plan to upgrade my heavy support soldier to the former.

Overall I've been taking a more leisurely pace in the game, I have full US coverage but have lost Nigeria so I can't get the +30% funding bonus (chose europe for my start). I've just finished the first alien base and it's research so now I need to build the hyper-wave decoder to activate the next plot mission. I've been enjoying it thus far and I've found that a Sniper, Heavy, 2 Assault, 2 Support squad really works well for me. I have a few more squaddies but I've been sloppy about getting a good number of backups trained but that is my next goal while I work on getting my satellite coverage up to 100%