One caveat:
to place Sell Metro order on NXT, you need to pay 1 NXT. To cancel and place new order, you need another NXT or two.
If you don't have any NXT, read carefully FAQ at the end of the guide, there's a way to buy a few NXT from the asset transfer bot.
They chose not the best option for buying or selling. For many newcomers like me, this innovation when trading will be very unusual. Hope no one will be angry and everyone will read the instructions before trading.
The most important thing is simplicity and when such strange things are brought to buy it certainly does not add to the popularity of the project.