UPDATE!
I've been wearing this holster for the last few days. Here is what I noticed over the last few days about the holster
Day One (Monday):
On Monday I had a meeting/seminar. For this, I had to wear a suit. I had on a sport coat, tie, white button up, white undershirt and khaki dress pants. From about 6am-8pm I had this holster strapped on with my S&W Shield. The majority of my day was spent in a seated position. 3 hours of it in a car and the rest of it in my meeting and seminar. At no point did my shirt come untucked from the holster, print, or become uncomfortable. Sure every now and then I'd adjust my waist line slightly, but I notice people do that all the time when sitting for hours on end. There was a lot of the day where I totally forgot I was carrying and the holster felt just as comfortable by the end of the day as it did at the start.
Day Two (Tuesday)
This day I did not have to wear a suit, but did wear a tucked in collar shirt and dress pants (much like my picture in earlier posts). This was another full day of sitting down (3 hours in a car). Being in Michigan, it was pretty cold, especially in the morning, so I did wear a pull over. When I got in my car to leave in the morning, I did look under my pullover and noticed my shirt had become untucked. Why was it like this? I'm honestly not sure. I remember tucking my shirt into the holster, but I also remember doing a couple practice draws before I left. Whether it became untucked because I forgot to tuck it back in or just happened, I'm not sure. For the rest of the day though, I did not have the shirt untuck though. Again the holster was just as comfortable and I had no issues with concealment.
Day Three (Wednesday)
Today I went to my place of work to meet with some people. I wore basically what I wore on Tuesday. The pants for today had the belt loop in the slightly different position, so I did move the holster a little closer to my belt buckle. I had the holster on from about 11am-7:45pm. I experienced no discomfort and continued to forget I was even wearing the holster.
Conclusion
I will say that I'm used to carrying a G19 in a JMCK The George as an EDC gun in street clothes. I don't really have discomfort issues with that, but I find carrying my Shield in this tuckable holster to be even more comfortable. I think a lot of it may have to do with the smaller size and thickness of the Shield and this tuckable holster REALLY tucks the gun in. There is absolutely no roll over. I'd say anyone who carries appendix and finds themselves moving their gun to a different position because they have to dress up will love this holster. There are no visible clips, the gun tucks in nice and tight, you have the ability to tuck your shirt deeply into the holster, and you'll forget it's even there. I highly recommend this holster and will be using it for when I'm wearing a tucked in shirt, which for me is basically everyday now.