I use Cliffords Flowers a few times a year and have always been pleased with the results. You can get $10 off your price if you order online - on any item - and their service fee is lower than the $18 or so I got whacked with once using FTD. One thing to note however is that on big holidays like Valentines Day or Mother's Day, it is not always possible to get things delivered on the exact day - especially if the delivery is to an office building.
Pros: nice phone staff and reasonable prices
Cons: sometimes busy on big holidays