BSD isn't that great on wheels, it won't last too long by itself. I don't find it that good on glass either. I like BSD on the paint though a lot. Persevere with the application method and it isn't grabby and doesn't need buffing. It's particularly good at reviving products that are just beginning to fail and will last about 4-6 weeks by itself.
I agree it isn't a QD though, it is a spray sealant used to compliment their sealant range, rather then to be used like classic QD's like Meg's Last Touch to wipe or clean a bit of dust, whilst not really adding any durability to the product.
Picked up a bargain in Tesco's on the weekend - Turtlewax Ice Synthetic Spray Detailer - Usually about a tenner in Halfords, got it for £2. Also got 3 bottles of their colour bleed wheel cleaner (like Iron-X) for £2 each as well. Both products on first investigation seem pretty good, with their detailer being more spray sealant than QD but being more slippy than BSD so will be better at cleaning.
Check out your local Tesco's, it would be rude not to at that price!