I carry AIWB almost exclusively. Subtle differences in holster design can make or break it for many folks. I prefer the JM Custom Kydex AIWB holster. The CCC Shaggy holster has also been well received. The good news is that as AIWB carrying has increased in popularity the market has responded with increasingly viable holster options.
It conceals very well (not just standing- seated, bending at the waist,etc), is comfortable, secure (allows for a two-handed defense), affords protection from bump-frisks, allows for access from under many cold-weather clothing options without having to unzip, allows access from the ground or against a wall, and it is fast - very fast (two handed draws are faster, one handed may be slower than traditional IWB).
It requires an un-tucked, closed-front shirt, is body type/shape dependent (it does not work well for people with guts or shorter torsos), it may not work well with ballistic vest (depending on body shape and fit of vest), one handed draws may be slower, and if you are careless with your trigger discipline, you may die.
An excellent discussion of the topic may be found here: