Not to intervene in this discussion but "Powergaming" is common throughout any tabletop/mini/wargame on the market. Most systems build it right into the model rules. Malifaux is no different in this respect. You have models with abilities or gear that when used in combination with other models/strategies (or what have you) that can seem broken or overpowered to new players or people that have never faced such a threat before. I think what the thread is trying to find is the fine line between "Powergaming" and "Cheeseball" (as my LGS calls them) players.
Most powergamers know the rules and their models akin to second nature and in most cases know what your models are capable of as well. This means they know both the strengths and weaknesses of their army choice and yours. Powergamers are usually competitive and play for keeps. This can seem as no fun to a new player or someone of the more casual nature to a game but a lot of this also comes down to the attitude of the powergamer as well (is he being a prick, nice guy/gal, helpful, etc.). Powergaming or "competitive" gaming is usually the next step up from the casual gaming side. This happens with time as you learn your models and rules. This is a natural progression as you get better. It is nothing to be ashamed of, but your attitude will determine how your opponent looks at you in the end.
Cheeseballs, on the other hand, are powergamers that take it one step too far. They also know their armies and yours and don't make choices on what is fun, competitive, and challenging, but rather go at it with the attitude of "how can I completely screw over my opponent". This usually constitutes finding the glaring weakness in your army and taking an excess of army choices to exploit your weakness (example: you have a heavy infantry army and they field nothing but area of effect/explosive weapons to wipe you out the fastest). Most "cheeseball" players in most cases will build multiple lists geared towards wiping out a specific army type and they have the tactic of seeming "polite" in letting you lay down your model choices first. Then they pull out their list they built specifically to wreck yours. This is no fun to face and gets quite frustrating really fast. I have watched players quit games completely after investing large sums of money into games because of "cheeseball" tactics and attitudes at gaming clubs. It is a sad but true outcome in many cases.
One more note to add to the "powergamer" versus "cheeseball" discussion: When you beat a powergamer they MAY get pissed (if they are that type) but they accept their defeat and move on. If you beat a cheeseball at its exploits they WILL get pissed and he will rag on and on about how the game is unbalanced or broken or how certain rules need to be fixed.
Just my two cents on the topic.