I own a m15-3, Great pistol. Its my altime favorite revolver. I prefere to carry it over my 1911(Gasp!!). Its been a great, and accurate shooter for me. Easy to carry and dependable.
Some things i can reccomend are find some aftermarket wooden grips that are relieved for speed loaders. The stock grips make using a speed loader dificult. Second, if it suites your fancy, have the cylnders chamfered. It will help somewhat with the loading process, especialy when using SWC bullets. Tho, I dont think it would be seen as a necessity. My m15-3 4" is at the gunsmith right now, getting chamfered. Tho, youll have to have the cylnder reblued, so that is a consideration.
For a good holster, check out the Bianchi Blackwidow. Great OWB holster for it.