I won't say that it is a bad thing nor will I say that it is a good thing.

Honestly, the reason why it uses the GNU C Compiler is simple. From the migrating.txt file for version 0.16b:
> Version 0.16 has some important changes that may break applications written for older versions of FreeBASIC (FB).
>
> There are no more plans to break compatibility from version 0.16 and up (unless the GCC (GNU Compiler Collection)
> back-end impose that, see the next paragraph), but FB been in beta stage, this kind of modifications should be
> acceptable. While we know they can cause trouble to many users working on medium-sized or large projects, be sure
> we tried everything possible before resorting to the final decisions.

> In the next releases, the plan is to move FB to become a GCC front-end, to take advantage of the endless number
> of platforms supported by the GCC back-end and the high-level optimizations only found in commercial and
> expensive C/C++ compilers. Some of the changes below were done to make the FB front-end compatible with GCC, the
> migration will take a lot of time and efforts from both the FB team and the user base, but the result will be
> worth.

I personally find it great. It makes it a bit easier to integrate FB with C. I just wish fbc would produce AT&T code instead of Intel code when it creates the ASM files. Intel is confusing to me, yet AT&T isn't.