I'm currently playing with second easiest difficulty. My first playthrough and all that.
I'm at mission 8 (where you are destroying Nerve gas storages) and I've only seen Thermotrons and one android to this point.

So, does the higher difficulty add more advanced enemies earlier in the game?
I really love fighting those mechs so I'm interested if raising difficulty adds more of them to the game.

I'm not sure about specific enemy types being added, but on no remorse difficulty standard guards will be using high-end equipment from the very beginning.

I've almost finished the game on loose cannon (3 lvl of diff) and I remember more than one android present in that mission. And if you want to know about this difficulty-enemies aspect. Start a new game on the easiest and hardest level - you'll see the difference :)

Beware: the game gets really tough on Loose Cannon and No Remorse difficulties!

Hah! I figured that much. I'm on level 9 and it's getting rough even on the current difficulty. Those Vetrons rocket launchers really bring the pain!

Strangely though I've never been angry when I'm killed. Older games just feel more... "fair" than modern shooters, even if they are relatively harder. Migh be a bit of nostalgia factor.
Still, can't wait to get on the Loose Cannon.

What's nice in Crusader is that the big difference comes from guard equipment. Standing in place and soaking up damage stops working when they blast you with high powered energy weapons. It feels more fair than a stat boost.

Descent had a very interesting difficulty system. The enemies fired a lot more often, with faster projectiles, and they became psychically evasive. Like Crusader, player was forced to improve tactics rather than just shoot them twice as much.

how are cheats enabled in crusader no regret??

Here you go.

Thank Half-Life for that because I'm pretty sure that's where all that started :(

PS. Remember Doom 2 where you got more enemies and even different types on higher skill levels?