I love Glocks. I shoot them and revolvers better than any other hand guns I own.
10mm- I feel perfectly fine with the 10mm for the reasons DK17HMR outlined. When loaded to top loadings it is a heck of a cartridge. Unfortunately the Delta is not up to handling the nuclear 800X loads.
Here are my thoughts on the leading. I use HI-TEK super coat exclusively so I don't worry about leading in the Glock barrels. Before I switched to HT I used speed green or Lotak Hard for my 9mm and 45 ACP ammo in the Glocks and never had any issues either. Fit is king blah, blah, blah.