I have not owned an XD40 SC. I have, however, owned an XD40 Service and an XD9 SC. If you're not used to .40 in larger pistols, I would not recommend it in the Subcompact.
That being said, I have only had a handful of failures in XDs, between my XDs and my father's (XD9 Service). Collectively, I've shot several thousand over the last couple of years, mostly out of my father's XD9. The failures I can remember were all failures to eject the spent case, mostly out of the XD40 when I first got it. I think that was an "operator error" or break-in issue though, because it disappeared rather quickly.
One peculiarity I've had that I'm not sure anyone else has is that with the XD's trigger, if I get too antsy and lift my finger off too quickly and don't follow through, I've managed to touch off an unintentional double-tap a couple of times. Again, it's operator error, but I find it amazing that I can bumpfire XDs on occasion.
The XD40 I traded off for the XD9 SC, and I find it to be easily concealable, even with a cheapass Uncle's Mikes Neoprene IWB. If you spend a little money and get a real IWB holster, it'll disappear nicely.
Accuracy out of the SC for the purposes for which it was intended is not a problem. A decent shooter can easily manage COM shots at 15 yards. I'm not the best handgun shot, but I can consistently keep about a 3-4" group with the XD9 SC at 7 yds. 25 yards is a long shot for that pistol, and beyond that you're just being silly with a 3" pistol, I think.
Biggest carry issue with an XD that I can see are twofold - since it's a single action pistol (it is, don't argue, anybody) some people may not be comfortable carrying it with a chambered round in front of a cocked striker. There is no manual safety lever, however I feel the the FP block along with the trigger and grip safety keep it safe enough. Secondly, sweat will cause corrosion to the XDs finish over time, so maintainance is an issue.
Also, if you get an XD SC, make sure you get the Pearce magazine floorplates for your SC magazines. They should just be required equipment, because unless you have little girl hands your finger will fall off of the end of the grip.