This sounds like a good enough deal to me.
Charge S$200 to ANZ credit card between now till 25 July 2012 and get a S$10 Isetan gift voucher.
This works out to be about 5% rebates but it is in the form of voucher and a Isetan one.
If you patronise Isetan often enough, it’s worth considering since this should be an extra benefit on top of any other card privileges.
Otherwise, if there is another preferred card that you have always been using that gives a better rebate percentage, then carry on.