Despite whatever the rep systems say about a trader, you still take a chance anytime you trade...I've had several hi-rep traders send bad keys, try to trade crap games for my top-tier stuff or scam me for extra keys by saying the key I just revealed and sent didn't work (although in one case it was true and I sent a replacement). For the most part the rep system can be pretty accurate when combined with amount of completed trades where no one has cried foul. I use SteamTrades and SteamRep in conjunction with barter.vg to help decide if I want to take a chance...+rep comments on Steam don't do it for me.