Thats not entirely true, although I'm on your side as I think its pointless, Intersango's new fee structure does make business sense: it delivers on the goal of reducing spreads. Their thinking is a tighter spread will lead to more customers. For those who unknowingly sign up, the buys will be more expensive then they expect. I think this is stupid, however it has made the exchange favour sellers. If you dont mind using two exchanges, you can use this to your advantage for your trading activities.
I think you're being imprecise with your word choices "favor sellers". It actually favors liquidity makers. They can be buyers or sellers, so long as they do not accept the bid/ask on the other side of the transaction.
The new system actually discourages participants from accepting a highest bid/lowest ask. Instead it encourages the order to be off that by 0.00000001 BTC (or whatever the lowest increment the market supports).
Hopefully the market throws a warning like "your commission if you click okay will be 0.095% which is equal to $x.yy . So the newbies don't get surprised.