1. Yes
2. Yes
3. InstantDEX gives you the ability to trade any Nxt Asset <-> any Nxt Asset automatically. Currently you can exchange mgwBTC <->Nxt and mgwBTCD<-> Nxt, but with iDex you can trade mgwBTC<->mgwBTCD, for example. Also, InstantDEX will support advanced tradebots.
Ahhh, because you can only list assets priced in NXT on the AE, which makes a market like mgwBTCD/mgwBTC impossible?
correct. NXT AE is fantastic, but has 3 issues.
1. it only supports asset/NXT orderbooks
2. it costs 1 NXT to place/cancel bids
3. you have to wait until the next block to know if your trade was matched
InstantDEX solves all this by allowing any asset/asset trade, it matches and locks the trades in seconds and there is no fee to place or cancel bids
additionally I added support for interfacing to central exchanges and it can even trade through to them automatically.
So, if you ask for an orderbook for asset/BTC, it will combinatorically search all possible combinations across N orderbooks in M different exchanges (in addition to direct InstantDEX orderbooks) and create a virtual orderbook that you can execute trades from
Think of InstantDEX as trading middleware. If there is a market, InstantDEX connects to it and creates combined orderbook.
BTCD/BTC will look at all BTCD/NXT, BTCD/BTC, NXT/BTC orderbooks and find the best price. This allows for single click arbitrage possiblities (across exchanges) from the GUI
I think it is fair to say that by using InstantDEX you will get the best liquidity and prices possible, since if there is an exchange with better liquidity/prices, I can just add support for that exchange and automatically all the orderbooks are enhanced with orders from that exchange
James