On a whim I put a titanium safety plunger in my Gen 3 34. Honestly, I can't tell a difference but it's been in there two years and hasn't broken or given me any problems. I think the only thing it really did was make my wallet a little lighter.
My favorite Glock to shoot is a 34 and that is what I compete with. However, in reality I shoot it no better than my mid sized Glock 23 so I wouldn't suspect there is much of a difference going to a 17.
I've built a steel threaded upper 22/45, a Pac-Lite 22/45, and a Ruger "Lite" for steel challenge and prefer the Lite by far to the other two. Maybe I'm just lucky but all three have been very reliable.
Competition Glock 34, duty Glock 21, and carry Glock 23. Although they are not identical they are all Gen 3 Glocks which I feel helps when changing from one to the other.
Looks like a Dawson STI/SV magwell to me. I've heard eard of them being adapted to fit glocks but never seen one.
http://www.dawsonprecision.com/ProductDetail.jsp?LISTID=80000C8B-1276884083
What are the chances of a stainless steel gen 3 Glock ice magwell in the near future? I've got an aluminum Ice magwell but would also like a stainless steel version for a little more weight without being brass.