I just played a very nice game, until my opponent (playing swamp and forest) played a trap. Since, between the two factions, there is only one trap, I knew immediately it was a waiting grave -- without even observing it had playing cost 3. As I had a slightly better board positing when it was played, I simply waited out until my opponent had to trigger his own trap.
I recognize that identifying things like this (and planning for them in deck design) is part of the game, but if traps are suppose to be "hidden", they ought to be hidden. With rare exceptions, unless jungle is involved, a trap is easily identified. This could be mitigated by providing every faction with a couple of more traps.
I think you new players will suffer at the hands of traps more, but experianced players will be guessing whats what. We didn't want too many traps per faction, but some could possibly use another trap each. I think steve has already designed extra traps for each faction in case we need more.