When it comes to primers I have to say that I really do believe they help your make up look better and stay on longer. Most of the days I wear eye primer under my eyeshadow and it does make a difference. You can see it as soon as you apply the shadow, colours are more intensive and vivid. Also they will stay on your lids longer. As for face primers, I do love them but I don't use them every day. The reason for that is because I don't wear heavy foundation daily and I don't like to add more products on my face if I don't need to. For special occasions (when I want to have perfect make up), or when I go out, know that I'm gonna pull an all nighter, when traveling, etc. I like to use a face primer. These are my all time favourites.
Bare Minerals-Prime Time (brightening) is probably the only primer I could use every day. It goes well under any kind of foundation: liquid, mineral, you name it, this stuff will keep it in place. I originally bought it to wear under my Bare Minerals Mineral foundation and been wearing it ever since. The trick with this one is to leave it on the skin for about 15 to 20 minutes before you do your make up. It will work wonders (meaning even out your skin and give it a dewy glow). Sometimes I just apply a little concealer on top of it and a bit of powder for a natural dewy face.
Benefit-That gal works almost the same as Prime Time, but it will give you nicer glow that will be visible even after some heavy duty foundation. Your make up will be safe with both  primers.
Revlon Photoready-Perfecting primer will transform your face into matte and even canvas for make up. Skin is very soft after applying it and your foundation will stay on longer and look great.
Sephora-Smoothing primer (paraben free), there is a version of this product that is not paraben free so check the ingredients when buying it. This primer is no miracle worker, but it doesn't claim to be. It will smooth your skin and keep your make up in place and that does make it an excellent primer. My foundation always looked fresh when I had this primer underneath. 
Benefit-Porefessional is not a primer per se, but when you don't want to wear primer on your whole face you can apply this just to the problematic areas and call it a day. It will keep oil at bay and, therefore, your make up in place.
Out of all eye primers that I like, Urban Decay Primer potion is my favourite to wear under matte eye shadows. I think that matte shades look better over this primer. For shimmery and shiny shades I recommend Artdeco's Eyeshadow base. Both are truly amazing primers.