The Comp-Tac Shirt Tucker is my choice. It is very easy to get on and off discreetly and that is important to me. My situation is that I carry TO work but can't carry AT work. There fore if I leave for lunch, I have to holster and unholster at least 3 times a day, sometimes in a public parking lot.
You cannot easily do that with a CTAC. It is a great holster, I have heard, for all day carry, but it just didn't fit my needs. The Shirt Tucker is easy on/\off, it is good at maintaining a stabel position if you have a good gun belt, it has a very good adjustable retention tension system, the Kydex is very fast to draw from (not counting getting to the weapon), the tuck-ability is very good and the weapon with a tucked in shirt and no jacket is very hard to detect (with some blousing of the shirt as Venus Pax mentioned).
While getting to a weapon in a tucked in shirt is not blazing fast, it is a heck of a lot faster that having to run out to the truck to get the one you left there because you could not properly conceal it.
I shoot IDPA matches with mine and it has served me very well. My approach to IDPA is generally to use the equipment I carry so I use my Shirt Tucker with a Glock 30 (subcompact .45ACP) in matches. While this is not the most competetive combination, it serves my purpose which is to get better with what I carry.
As to how it works, think of a conventional IWB holster. To use it with a tucked in shirt you end up with a wad of shirt tail where the belt clip attaches directly to the holster.
The design of the tuckable holster is that rather than the belt clip attaching directly to the holster, it attaches to the top of a skinny U-shaped piece and the other top of the U-shaped piece (called a strut) attaches to the holster. The narrow void between the inside of the pant waist and the holster is where the shirt is tucked...avoiding the bunching around the holster. It is sort of like an inverted paper clip with the shirt going where the paper would go..
I am sorry if I am not explaining it well. You may have to just see one. Since you are so near Houston, contact Comp-Tac and go in to see them. It is just up I-45 from you in Spring. Here is their website. Contact them and you will find them to be nice folks with very good customer service.
I would also recommend getting an extra strut so that if one breaks, you are not out of commission until a replacement is obtained. You might get one in a different size so that you can use different size belts. I use a 1 1/4" belt/strut generally but I also have a 1 1/2" strut I occasionally use.
I might add that it works very well as a conventional IWB holster under a jacket, vest or long T-shirt or untucked, open shirt. That is how I use it in IDPA.
I hope this helps. (no, I don't work for them...just a believer) Good luck.
http://comp-tac.com/