I have had only one bad experience with the GLC-EX-SM1550-40 transceiver bought from FS.COM—slow delivery. I told them about it and got IMMEDIATE satisfaction. The reason is because they were on holiday to celebrate the new year! Great place to do business.
I have installed the 1G SFP EX transceiver to Cisco SFE2010P switch and Blackbox LIG1014 switch, it works good. The shipment is fast, and the customer service is very attractive. Great Service, Great Product!