We use both the vikan and unger kits, not a lot to choose between the two, vikan pads are good all rounders, unger do several grades which perform well and they do a heavy duty pile which is great for really dirty stuff.
You can easily go through 40+ in a day ( schools - hospitals etc ) if he windows haven't been regularly cleaned you sometimes need to go over them a second time - tadgh's waffle cloths work well on the pad holder as well.
Darran