Where I think the time unit thing really really falls short is when you're on a "terror" mission. That's where the aliens are just in a city killing all the civilians in sight. You can save civilians by moving a unit adjacent to them. First problem is that with no time units and no way to designate waypoints you can be in a room full of civilians but can't move next to each one even if they are well within your units movement area. So if you move one step to get right next to one guy that'll take an entire action for that turn and you can burn your second action moving another step to save another civilian.
I guess the inability to change course if aliens are spotted during your unit's movement is also related to the elimination of time units. It sucks pretty bad, especially if you've inadvertently moved your unit into a nest of aliens that you couldn't see before.
I couldn't help but think during missions that even in Apocalypse (I never played the original, but got hooked on Apocalypse) the firing actions were more realistic. Part of that, again, is related to time units. In that game some weapons required very few (sometimes only 1) time units per shot. You could continue to take shots until you ran out of ammo or ran out of time units. Or, if you wanted, you could stop firing from that position and move in for a better shot or move back behind cover. Shooting seemed pretty realistic. In this game it couldn't be more obvious that it's a dice roll. I know it essentially always was, but in this game you're not going to accidentally kill other aliens in the vicinity. In fact, if there is an alien standing directly in front of the alien you target your shot will go through that alien and either kill or miss the alien you shot at. In the old game with the machine gun or with the bio-gun I'd often pick an alien in the middle of a group and start popping off rounds. I might not hit the alien I was shooting at but the bullets would often strike the other aliens. Then when I was down to only a few time units I'd move back behind cover.
The thing with cover is bad. When your unit is about to take the "fire" action you hit the fire button and a target pops up with a percentage representing your chance at hitting that target. Often something that is close and easily visible has a low percentage but something that is far and completely obstructed from view has a high percentage. There's very little way to know without pulling up the targets one-by-one to determine if you have a good shot at anything. This goes both ways. You can't be sure where you're moving your unit is safe. I had a sniper back behind the front line, in an elevated position and behind half-cover. My assault and support guys were in front and performing the "overwatch" action (you can end a unit's turn who still has an action remaining with overwatch and that unit will fire during the aliens turn at the very first thing he/she sees). The aliens didn't technically move but began shooting at my sniper. A few lucky shots later and one of my most valuable soldiers was killed.
That brings me to another gripe, which is again related to the time unit thing. When your unit shoots he/she moves out of cover as part of the "fire action." So when these aliens started shooting at my sniper they "moved" from behind a wall and shot, only because they didn't technically move my units in overwatch didn't return fire.
Map size. Yeah, the maps seem big in a way, but units are about 4x as big compared to the other objects as they seemed to be in apocalypse, so the maps are really pretty small. It eliminates the frustration of losing a brain sucker and splitting all your soldiers up to go hunt it down, only to have it brain-suck your highest ranking soldier, but it doesn't feel like to wide open world the other game did.
Also, every mission is at night. They are trying to recreate the shock and terror of the old games by making things dark. It doesn't work. In the old game you could walk past an alien sitting behind a potted plant if you didn't turn a unit to face in that direction. The fun was when you did turn around after spending all your time units only to realize he was right behind you and he's going to kill you now. In this game you don't have to worry about facing your soldiers. They see aliens in 360 degrees.
So, these designers made a compromise game. It isn't believed that a true TBS game will sell. Maybe it wouldn't sell well, or play well, on consoles. I'm getting pretty tired of no games being made to the strengths of the PC. Amazing things are possible, but if it can't be directly ported to Xbox and PS3 then it isn't going to happen.
Despite the gripes, the game is still pretty fun.