I'll just say that my views come mainly from experience, specifically ECL (Embeddable Common Lisp, a CL implementation) and (this was further back, so my memory is fuzzy) a tool for generating executables from Perl scripts. I don't think I'm using an especially unusual setup, or unusual compilers, and I would guess that these tools probably target a very narrow subset of C. Despite this, my experience with these sorts of tools has been anything but "works out of the box". On the contrary, there appear to be a great number of degrees of freedom, even with standard-ish setups, that can trip up these tools. Because of the additional layers of abstraction, the error messages you get are very poor. Some header file is missing or in an unexpected place, or worse some generated code fails to compile. As an end-user, it's basically impossible to debug these in a reasonable way.
You can certainly have internal errors using LLVM, but in my experience fewer of them are platform-dependent. Therefore there is a greater chance that something that works for the developer will work for the user. Also, if error handling is done properly, if a failure does occur it can often mapped back to the original source program. This is much better as far as usability goes, since the user almost never wants to debug some compiler's generated code.
I'll just say that my views come mainly from experience, specifically ECL (Embeddable Common Lisp, a CL implementation) and (this was further back, so my memory is fuzzy) a tool for generating executables from Perl scripts. I don't think I'm using an especially unusual setup, or unusual compilers, and I would guess that these tools probably target a very narrow subset of C. Despite this, my experience with these sorts of tools has been anything but "works out of the box". On the contrary, there appear to be a great number of degrees of freedom, even with standard-ish setups, that can trip up these tools. Because of the additional layers of abstraction, the error messages you get are very poor. Some header file is missing or in an unexpected place, or worse some generated code fails to compile. As an end-user, it's basically impossible to debug these in a reasonable way.
You can certainly have internal errors using LLVM, but in my experience fewer of them are platform-dependent. Therefore there is a greater chance that something that works for the developer will work for the user. Also, if error handling is done properly, if a failure does occur it can often mapped back to the original source program. This is much better as far as usability goes, since the user almost never wants to debug some compiler's generated code.