It hardly involves 'wallhumping', at least not as much as an actual cover shooter.
There is no actual cover mechanic, it just stands to reason that keeping something between you and the people trying to shoot you is generally the best way to not get shot.
I kind of find it sad that so many people would turn to Youtube playthroughs of it instead of buying it. That would seriously defeat the point of a game for me... Sure, maybe some people can't afford to shell out to buy a PS3 for a single game, but hell, I have never played the Portal series, I cannot afford a computer capable of running it, but I'm not going to just ruin the game for myself.
As for the shooting gameplay being poor-- let me just say, it is 100% up on Uncharted. It's nowhere near as painful, and any AI allies you have tend to actually help you, for a change. All the other parts of the gameplay, the stealth, the exploration, those are all excellent fun. If it takes a couple of shots to kill a baddie, is that really a dealbreaker?
Also it has the best (yes, best) online multiplayer of any shooter/action title I've played. Only MGO can even come close, and that's been dead for years. But anyway, even if you don't have a playstation and do not want to buy one, why spoil the game for yourself? Who knows, maybe you might have/make a friend with a PS3, or you could rent one, or you might somehow acquire one somewhere down the track.
I just don't get why people would avoid playing games by watching someone else play them instead.
I've never done that.
I just wait until I have a chance to play these critically-acclaimed games that I miss out on for various reasons.