I used to study tactics with CT-Art (an excellent program). Within the last month or so I've switched to PCT. You can see my most recent history.
What I like about PCT is that it includes an endgame component. By studying the endgames with PCT, I feel more knowledgeable and confident with that phase of the game. I feel it's also changing my game. I no longer feel that I have to blast my way through the middlegame with some amazing tactical shot, but can move into the endgame (or at least some endgames) with a good chance of holding my own.
Regarding middlegame tactics, since using PCT, I feel like I'm seeing more in blitz games on ICC, but the real test is OTB tournament.
I just started a quad yesterday at the club (drew a 1780). I'm the lowest rated in the group, with the highest rated having an 1800 floor. So, I've got a great opportunity this month.
One of the things I've concluded about chess is that it's less about winning, or may be I should say, less about forcing a win by brute chess strength, and more about not losing, more about waiting for your opponent to blunder. "Waiting" sounds passive, and that's not what I mean. You can't just wait, you must test your opponent, and you wait for a wrong answer.
If you can get the initiative, and set problems for your opponent, even if they're not difficult, then you have a far greater chance of winning.
It's like there's a conversation going on between the two of you:
White: One plus one equals... ?
White: Tweleve squared equals?
Black: Uhh, 143?
White: Close, but no, I'm sorry. Now, Estne Roma in Italia?
So, you definitely want to be the one setting the agenda, by having the initiative and asking the questions. If you're the one being asked, then you'll have to come up with the correct answer and that's always tougher.
I guess beginners play chess like babies:
White: Agie mee ta gee doh?
Black: Og me oh beee bboo
By studying tactics and patterns, you are learning the questions and the answers that will be the conversation of your game.
Anyway, I like the language analogy.