Yes, I own a Ruger SP-101 and have carried it concealed.
Originally, I purchased a used SP-101 chambered for .357 Magnum.
After firing some .357 Magnums through it for target practice, I decided that .38 Specials were much more pleasant to shoot through it.
Eventually I traded it in for an SP-101 chambered for .38 Special. [I got annoyed with cleaning the 1/8" long rings of carbon fouling that formed inside the cylinder chambers. I'm picky that way. It wasn't the guns fault. ;-)]
Okay, now for the opinions of how well it shoots and how easy it is to carry.
~ The Ruger SP-101 is an accurate snub-nosed handgun. At a distance of 10 yards or so, mine will produce shot-groups measuring 2-3 inches in diameter. Beyond that, shot-group sizes open up and at 25 yards the shot-groups measure 12 to 14 inches in diameter. This is due to a combination of factors which include a short barrel, short sight radius and the ability of the shooter to keep the gun steady.
~ The SP-101 is built like a proverbial tank. It is hefty for its size, and that heft inspires confidence.
~ That extra heft makes the SP-101 more of a burden to carry when compared to the S&W Model 60 or the Taurus Model 85. But the burden is reasonable and bearable.
~ The SP-101 is reliable. The most I've fired though mine during a single range session was 200 cartridges. It was dirty and gritty, but it still functioned properly.
~ With OEM grips, the SP-101 works well with speed-loaders made by HKS or Safariland. With non-factory grips, some modification may be necessary. I had to modify my Pachmayr grips by removing some material.
~ There are more SP-101 holsters available now than were available 10 years ago. That said, you may still have to shop around to find holsters you're happy with.
~ Mine has a 2" barrel and that size is easier to carry concealed, especially when using a pocket holster or ankle holster. The 3" barrel length is less of an issue if you carry inside the waistband, but the 2" barrel offers more concealment options. Also, the longer barrel will be heavier and more of a burden to carry. Since the 2" barrel is accurate enough, why burden yourself?
~Ergonomics. The Ruger SP-101 is very "user friendly". I prefer the cylinder latch button of the SP-101 more than the Ruger LCR's method of opening the cylinder.
The trigger pull of the SP-101 is very reasonable and it gets better with use. Keep it clean & properly lubricated and you'll be a happy SP-101 owner.