I fully agree with hyperbob on how some of the 'gamey' strategies ruins the flavor the game. Using ahistorical but plausible strategies are is IMO (like opting for Sea Lion, or making a stronger commitment to taking Africa or deciding to implement the ideas for the 'Z plan' and win naval war). Those are all things that are completely plausible within the framework of WW2.
Things like hyperbob mentions like killing off your own Infantry to take advantage of cheaper research is simply exploiting the game mechanics. Yes it works, but it is beyond silly when considered in any form of realistic framework. Like hyperbob, things like that kill my desire to want to play against other 'skilled' opponents. If I want to look for cheap exploits, I'll play Warcraft, Command and Conquer, or Madden 06 online. When I sit down to play a game like W@W, I want to pit strategy against strategy, not gimmick and gimmick.
Obviously people will disagree on what is an exploit and what is a clever strategy (as people did when the 'Neutral Hunting AV' was all the rage). One man's cash is another man's trash. That makes it even harder to agree on what is 'legal' and what shouldnt be.
I definately applaud 2by3 for trying to remove some of the early gimmicks that have come up (Italian 'gambit', Prussian attack, Japanese bombing etc), but I know that some of these 'strategies' are going to be next to impossible to eradicate. I find that unfortunate.
At one point I was really looking forward to TCP/IP play to 'broaden the horizons' of the opponents I could play. Now that I've seen what occurs in games between 'good' players, I'm less enthused and I'll probably stick to my own little crowd where we play competitively, but within the spirit of the rules, not the letter.
Anyways, that just my own $.02.