On the surface, 150 points for a $20 FTD code, discounted from 400 points, seems like a pretty good deal. A quick search of the web, however, would reveal that a $20 discount at FTD is a bad deal at any price, given how many discounts there are, unless you are buying a lower-priced item, particularly given their quality. I'd hold back on this one.
By the way, for those of you looking to buy flowers on the internet, I've had good results with Teleflora. Cashbackaholic notes that you can get up to 20% back at ebates, although I'm sure that there are other coupons out there.