...The only problem you may have as mentioned above is the rear sight retaining pin may break or work out and eventually you'll lose the front sight if you shoot it a lot. These problems are very common with the Colt Series 70 GCNM but are easily fixed.
That has been my experience too. The last time I put a front sight on my gun I installed it with red Loctite and swaged it, which seems to have helped. One could have the slide machined for a cross-dovetail front sight, but I don't think it is worth the bother. As to the rear sight, years ago I read somewhere that the "fix" was to use the shank of a tight fitting drill bit to make the replacement pin. That has worked well for me. If you do that, be sure to buy a US-made drill bit rather than an import-cheapie. You cannot count on the quality of the steel and heat-treatment being the same with inexpensive import drill bits.
The hubbub about the Series-70 collet bushing always amused me. I have three Colts with that bushing, the first purchased in 1977 and all still in use. They all have been shot - one of them quite a lot. All have worked fine since day-one, and they have been noticeably more accurate than the older guns without the collet bushing - the ones that I have experience with, at least.
My particular Series-70 GC had only one major flaw and that was the serrations on the face of the trigger were so rough and sharp that eventually they would make my finger sore, and then I would think about that instead of paying attention to what I was doing. I took the plunge and polished the serrations off the trigger so that it is completely smooth, like an S&W "Combat" or "Border Patrol" trigger. That solved all my problems. I shot the gun weekly in an informal indoor league for about 5-years - no problems other than those mentioned.
My only "complaint" is that the gun doesn't have a checkered front strap, so I always used (ugly) Pachmayr grips.

And of course the little depressor and spring make re-assembling the gun after cleaning a little more challenging than an ordinary 1911. You can make a little slave pin from a brad to keep everything in place which you just push out when installing the sear pin. That takes most of the misery out of that process.
I like the Series-70 guns just fine.
