I wouldn't trade my early R9s (serial # R3xx) for any other gun. Last year I bought a Ruger LC9 for those occasions when I wouldn't want to risk the Rohrbaugh, but found it doesn't fit as easily in the pocket. As good a shooter as LC9 is, compared to the R9s it feels like a clunker. A clunker with a somewhat weird trigger. Especially compared to the R9. I take that back - no other pocket-size gun compares to the R9 trigger feel. That's what sold me on the R9 back in 2005 when the late John Johnson let me handle and dry-fire his sample R9.
There is currently an empty spot in safe for a .40 S&W pistol, as I finally broke down and gave my 1994-vintage H&K USP to my son. That S&W M&P Shield in .40 S&W may be a good replacement as it is much more suited for concealed carry than the duty-size USP.
My nephew picked up a Shield in 9mm. He owns quite a few high end pistols and really likes the Shield for those quick trips to the store, etc. The only reason he didn't buy the .40 Shield is his gun shop couldn't get hold of one for him.
I'd probably wait another 3 to 6 months before buying a .40 S&W Shield. Been burned several times by my impulsive "need" to have the latest and greatest pistol (and car, and computer....)
Steve