Think I'm obligated to weigh in here, since I've spammed this forum with gun porn of my PTR more than once...
I obviously like my PTR a lot. Mine's been customized a fair bit, which is one nice thing about the PTR series guns: they're built close enough to HK specs that all sorts of parts from various guns in the family fit right on them. I have the cocking lever from a 21E LMG, the recoil buffer from a PSG-1, and a clipped trigger pack from a G3 with a trigger job by Bill Springfield.
The recoil really isn't particularly hard, but the characteristics of the recoil impulse with the basic G3 style recoil buffer are uncomfortable to a lot of people (think giant nail gun; ka-CHUNK!). With a longer/heavier buffer, like a PSG-1, 21E or 2-stage heavy buffer, it's a pussycat. With my PSG-1 buffer it's a long push feeling, noticeably less sharp than the recoil of my friends M1A.
I don't personally mind the mag release, but I have big hands.
You'll want a trigger job. Stock is usually about 7-8lbs and creepier than your uncle with the lazy eye. My trigger breaks at about 4.5lbs and with a minimum of creep.
As mentioned previously, if you reload, or might someday try, then get an ejection port buffer. RTG has POF copies of clip on HK buffers for $35 right now. It will pay for itself in brass in a couple range trips.
CTD had mags cheap, last time I checked. I ordered 40 steel ones for $2 ea a few years back. They've gone up since then, but still a lot cheaper than the $20 ea that seems to be the going rate at gun shows and shops, that I've seen.