Still, this is only really an issue when your team isn't working together. And even if you're playing with random Internet folk, you can jerry-rig a form of teamwork by watching what they are doing and adapting your approach to accommodate. If they set all up to attack a room from one direction, for example, it's often a good idea to flank from a different direction. Teamwork comes even easier when defending, as most of the time the squad will consolidate their defences in a single room, filling in any gaps naturally and avoiding obscuring lines of sight.
It helps that it feels good to do most of these things. Setting up barricades and deploying cover has a satisfying tactility to it, as does planting breaching charges to obliterate those defences. When the explosives go off, walls and barricades shatter into a cloud of splinters, kicking dust into the air that obscures the view of both teams. The actual shooting is still a touch on the lightweight side, and I find that the guns take up far too much screen space. But it does the job well enough.
Regardless of audio/visual satisfaction, the emphasis on destructible environments makes for an intriguing tactical challenge. As an attacker it's all about finding the right entry point, rolling your camera drones beneath the barricades, scouting out enemy positions and trying to identify and ideal breaching point before the defence spot the drone and destroy it. The moment when the breaching charges detonate and the bullets start to fly is utterly exhilarating.
If being an attacker gives you cause for apprehension, then being a defender is positively terrifying. For you there is no escape, and any cover you find is no guarantee of protection. Bullets carve through most objects with ease. You can even shoot gaping holes in walls and watch for enemies through them. Mostly though, there's little to do but wait for the inevitable fireworks to kick-off. Ubisoft knows how to rack up the tension too. You can hear the opposing team moving around through the walls, the thudding of their footsteps on the floor above you, the distant shattering of windows, the dulled concussions of faraway explosions.
But the real star of Siege isn't the gadgets or the destruction. It's the level design. From hotels to farmhouses to aeroplanes, each is a superbly designed maze of rooms and corridors. It's also here where the game most resembles the tactical shooters of yesteryear, particularly Irrational's exceptional SWAT 4. The complex architecture, carefully cluttered with objects, means lines of sight are always short and rarely clear, and every blind corner represents a potential deathtrap. Moving carelessly through these spaces will almost guarantee you an early exit from the game.
While the multiplayer is undoubtedly the main draw, there are a couple of alternative modes. "Situations", is essentially a loosely connected tutorial campaign. Playing as a single CT, you must navigate your way through a sequence of increasingly difficult missions, clearing each area of terrorists while the game instructs you on a particular mechanic. It's a perfectly acceptable introduction to the game, but don't expect any more from it than that.
Then there's the return of Rainbow-Six staple Terrorist Hunt, which can be played either cooperatively, or single-player in Lone Wolf mode. However, it's undoubtedly designed with cooperative play in mind. Played solo, it's tougher than a tardigrade. The bomb-vest wearing enemies are especially horrible to fight, especially in a game where the majority of encounters are at close-quarters. Frankly, I think I'd prefer the game without them, as being killed by one always feels cheap.
Lastly, and it's possible that I've missed something here, but there seems to be no opportunity to select what map or game type you play, whether that's in a group with friends, or voting for a server after a match. It's not a massive issue, as most of the maps are fun to play on, but it is something of an oversight that ought to be rectified.
Mainly though, Siege either smoulders or sparkles relative to the skills of your team. If, somehow, you can get ten friends together to fill out a server, you're in for an absolutely fabulous time. Playing with the freakishly talented or simply freakish kids in the great ball-pool of the Internet, it can go either way. You'll still be in for a blast, it just might not be a blast that's in your favour.