You can buy Blocknet tokens using any participating coin.
At Bter and Bittrex there will probably only be a BTC:BLOCK pairing.
At Poloniex there will probably be a BTC:BLOCK and NHZ:BLOCK pairing.
At CoinGateway all the other coins will be paired to BLOCK.
After the ITO, only BTC:BLOCK pairings will be available (because it makes no sense for participating coins to trade against the Blocknet when they function to give value to the Blocknet).
could you please explain how the 10 % discount using any of the participating coins will be managed exactly?
considering for example the nhz:block pair on poloniex when and how will the its price be determined? will it be a fixed price or will automatically adjust to the current btc:nhz price?