This problem also appears in other forms. One part in particular was especially jarring. I was boosted into the window of a house which I had to clear. After clearing it I realized that I was alone and that my squad was no where to be seen. I made my way downstairs and there was my squad, all ready to go. How'd they get in? I have no idea. Sometimes you'll move too fast, sometimes you'll move too slow, and either one will result in you ending up alone and then magically finding your squad intact elsewhere waiting for you to join them. It feels very artificial, and while it doesn't ruin the game, it does tarnish how immersive the experience is.
Maybe it's a good thing that your buddies aren't always around. There were more than a few times when my squad mates would bunch up in a stairwell or in a narrow alley. This is only a minor annoyance when you're not under fire, but when Jerry is about, it can easily lead to getting shot while you desperately urge your men to get out of your way. Some annoying collision-detection issues only make matters worse. There will be times when you'll be walking along and a metal plate on the floor that looks only one or two inches thick will prevent you from moving on. Instead, you'll have to walk around or jump over it. Once again, this typically isn't a huge issue until it happens to you while you're desperately making your way towards cover while under enemy fire.

This gets even worse thanks to the real-time physics for debris from explosions. Sometimes you'll be crouched behind cover and able to move freely, and then a building will explode near you. A plank of wood may fall behind you or to your side, and you'll discover that it prevents you from moving around. There was a moment when I was stuck for a good five seconds by a piece of debris before I could move on. I can think of at least three specific times when I was stuck in the environment and unable to move and ended up getting killed as a result.
Your enemies are as formidable as ever, but they're also dumber than ever at times. For the majority of the game, the enemy AI will act like the well-trained army they're supposed to be. They'll use cover, fall back to better firing positions, use grenades smartly and toss back grenades you send their way. Unfortunately, there were a few times when they seemed to shut off their brains. In one level I had to hold a tavern from a German attack. The first wave came from the north, the next came from the south.
The northern wave was tough, but the southern wave made it into the building by droves. However, once they got in they seemed to forget that there was a war on. I was caught with an empty clip in my rifle and had to reload. The Jerries seemed perfectly content to just stand there and watch. Not a single round was fired in my direction and I was only a few feet away. Typically, when you're this close the AI will shoot you or hit you with a melee attack. These guys just stood there. It wasn't until I dropped a few of them that they actually started to fight back, and by then it was too late. I thought this was a one-time glitch, but it happened when I replayed the level as well. Perhaps it was because I was positioned awkwardly on the second floor and shooting down at them, or maybe it was because there was a smoke grenade going off nearby. Whatever the cause, it made me feel like I was playing an unfinished game.