The array that you pass to the -datastores parameter can have multiple datastores in it. For example:

GatherIOPS.ps1 -server myvcenterserver.mydns.com -datastores @("DS01","DS03","DS25") -numsamples 90

Currently, the script will only work against one vCenter instance (but gathers data from all ESX hosts managed by that instance). If there is a need to hit multiple vCenter Servers I can modify it to take this in as an array as well.