IOPS= Input/Output Operations per Second. It is the number of individual input or output requests the drive can handle per second, the higher the number the better. It is a way of measuring the drives performance, different than throughput which is the amount of data the drive can move in a second as opposed to the number of operations.
To answer your second question, ook at the Intel 520, Samsung 830 or it is a great deal, the crucial m4. Honestly, I highly doubt you will notice any difference in real qorld performance since SSDs are so quick in general.
The intel/samsung will have slightly better performance, not that it really matters. I have an m4 that I'm extremely happy with, that's the only reason I included the crucial. I wouldn't say the corsair or OCZ are "bad", but I've heard nothing but good things about the intel and samsung, I can't say the same about the corsair or the OCZ. I know earlier generations of those drives had issues. From a reliability standpoint, I would go with the Intel personally.