I enjoyed it quite a bit. ESPECIALLY the expansion. The Enemy unknown felt a little lackluster, but Enemy Within adds the extra cool stuff that has me going on marathon, even though I still cannot beat classic. It's still too brutal for me. :<
Once you get the formula right, Normal's too easy, but classic still too hard... I should do a lets play with it too. Get some people talking while I do it. ^.^
Also, I've seen mention that Aliens never ambush you. I'm gonna call such hard bullshit on that. I've ambushed aliens,(Before the pod activates, but attacking them triggers it.) and they've ambushed me. I think the current format is best, because when you're fighting enemies to the west, and enemies from the South come in and blindside you? You get the "pod activated" animation, and they all immediately get in position. Some in sight, some out of sight. And they all shoot at you next turn. I've been shot at numerous times when solders are not hunkered by an invisible out of sight enemy. They're normally misses... But one or two of them have hit. Taking on 9 aliens at once, team of 6...? Not easy, even when the game cheats for you on normal.
Tips for classic I've seen though?
Don't shoot unless your hit% is above 70.
Don't attempt to flank until you've got 6 marines. My "pod emulation" tactic seems to go fairly well. (Two closely knit groups of three, they meet up at the end of the level.) Flanking with 4/5 marines means your lone guy, or group of two could activate another set of aliens, and now you're up against 6.
Only use partial cover when you haven't activated an alien pod. When your stuck in partial cover, Hunker.
Actually, hunker, hunker, hunker. If you think someone's going to be targeted a lot, hunker. Someone in partial cover? Hunker. Civilian? Hunker. This is the biggest hurdle for me, because I saw hunker, and thought "I'm not attacking and this blinds me. It sucks." The extra bonus is worth it.
Overwatch. Have at least one person overwatching at all times.
Split up. The AI is "unshackled", which means there's no restrictions on their items now. (one grenade collectively only, 10% chance to actually go through with it.)
*** Also, in case your wondering what a pod is... ***
The AI doesn't manage the aliens individually all the time. It has groups of up to three aliens moving around the map, or remaining stationary. Maybe we have three sectoids moving around, or an outsider standing still.
When the player sees a pod, the pod is now active. A "scurry" AI takes over, which forces the aliens to use 1AP to hide, and get into some random cover. Often, they'll choose partial cover. On easy, they might "forget" to do this.
On the next turn, the AI based on difficulty takes place for each individual alien.