FYI, Just wanted to post my experience. Love PMS, my primary media server for quite a while now. I've always had a bit of stuttering in my HD videos, especially when I stream wireless to ps3 (PC is wired to router) ( i would watch the PS3 info screen MPEG2 kpbs increase to about 40.0 or more before I would see stuttering using PS3 wireless.)
Thought I'd try optimizing a few settings and first updated my PMS from 1.54 to whatever is current today 1.71, also update Java from version 7 update 5 to version 7 update 9. ALL PMS SETTINGS WERE SAVED / NONE MODIFIED.
I now have the constant video lagging problem i've seen expressed elsewhere, my HD videos stutter MUCH less, but the video starts falling more behind each second. I've also noticed in these cases the PS3 info screen would never show the MPEG2 kpbs exceed 10.0 on the exact same video clip which would exceed 50.0+ on old version. Also ... subtitles started appearing uncontrollably even though I have definitely disable subtitles checked.
Uninstalling 1.71 and redownloading and installing 1.54 instantly solved all problems.