Think of this as a spray on primer come setting spray. You mist this on before make-up (I do still apply primer on top of this to fill in open pores) and again once you have finished your entire look to set everything in place (I do not use this in place of powder). I find this weightless spray keeps my foundation fresher for longer, doesn't fade, become patchy and oil is more controlled than usual (my cheeks do become a little oily as does my t-zone after a few hours). It is very much the same thing for blush, bronzer and highlighter be it powder, cream or liquid. I am afraid I don't find this does much for my eye make-up and do tend to use a "normal" primer and steer clear from misting this near my eye area. I don't use this daily but do rely on it if I have to be out all day and night without the want nor means to constantly re-touch my make-up. For a night out or those who just want their make-up to stay in place all day long (I'm talking a good 10 hours for normal/dry skin and around 8 hours for oily skin) you really can not fault the Urban Decay All Nighter Makeup Setting Spray. Although it does over slight oil control if living in or visiting humid conditions or you have super oily skin I do not recommend this over the Urban Decay De-Slick spray. Generally speaking this is perfect for normal to dry skin types looking to prolong make-up wear, oily complexions can still benefit from this but I would recommend pairing it up with Urban Decay De-Slick spray for reassurance.
Again this is a lot like a spray on primer perhaps more so than the above mist as it has been created to control excess oil. Much like the All Nighter spray this is applied before and then again after make-up application to both control excess oil and somewhat set the make-up. De-Slick is light weight and won't clog the pores but rather keeps oil at bay without encouraging the skin to dry out which I find rather clever. Yes this will help make-up stay in place to an extent due to it mattifying the skin and preventing make-up from sliding off the skin but this will only really work if you have oily skin, otherwise I highly doubt you will benefit from this mist. Yes it keeps oil at bay but if like myself you find yourself touching your face a lot or y'know falling asleep on the bus etc and don't want your make-up to transfer you may want to apply a quick spritz of the All Nighter on top to really keep everything in place. I do double up if I have a long day and/or a night out. Having said that I do recommend Urban Decay De-Slick over All Nighter for oily complexions.
In a nut shell? Urban Decay De-Slick for oily skin types and Urban Decay All Nighter for all don't want their make-up to budge full stop.