I've been using regular non +P loads in my 642. I tried the Speer Gold Dot 135g +P for short barrels (actual 1 7/8" barrel - just like the 442/642) and I found them to not seem any more powerful than the non +P loads. I have yet to shoot it through my chronograph as it has been just too cold outside to do any serious shooting and setting up necessary equipment to do so.
I tried wooden grips from S&W because I thought the rubber grips would snag in my pant pocket, but the Uncle Mikes #59010 OEM rubber grip is just fine. I use the Robert Mika pocket holster and the gun is quick to draw. I tried the #3 Uncle Mikes SideKick Pocket Holster and every time I pulled the gun from my pocket, the holster stayed stuck to the gun. That will not happen with Robert Mika's holsters, for sure.
I have the #36 HKS speedloaders which work just fine with both the wood panel grips and with the OEM Uncle Mikes rubber grips. The rubber grip gives me a bit better hold as it is a bit wider (front-to-back) but is not quite as long as the wooden panels. The wooden panels cover the bottom strap of the grip handle whereas the Uncle Mikes 59010 OEM grip leaves that bottom strap exposed (you can see the serial number on the bottom with the Uncle Mikes grip, but not with the wood grip panels). In what little shooting I have been doing out in my barn, I found that the OEM rubber grips are a bit more comfortable than the wood panels. The wood panels did hurt just a bit, however I am used to shooting a 500 Magnum - 4" barrel.
In my opinion, the Uncle Mikes OEM (59010) grips are the ones to use and keep. If you want the Crimson Trace laser grips, then that is another story altogether, however the thought of relying on something battery-powered doesn't turn me on.
I did try the Tyler T-Grip adapter along with my wooden panel grips, but they did not fit and I had to send the T-Grip Adapter back. The problem was that the S&W wood panels were not exactly flush along the front of the gun grip frame (Tyler DOES SPECIFY THIS on their website -- that the existing grip has to be flush in the front where the T-Grip will meet the existing grip panels - in other words, no metal grip frame showing along the edges but instead, the panel coming right out and meeting the very edge of metal frame all along). When I installed the T-Grip Adapter, there were unsightly spaces where the wood panels should have met the adapter. Tyler was very good at taking it right back and giving me full credit (less shipping if I remember correctly), anyway I was satisfied enough with them that I would definately consider the Tyler T-Grip and their other products again as they were extremely friendly, helpful & courteous!