I don't use MAC mascaras very often, though I do like a few of them (fibre rich & zoom lash). Other than that I mostly have MAC, but not entirely. If there is a colour I want or something I find is better in another brand then I'll get it, I do tend to be very picky about e/s unless it will fit in my palettes though, which is more an issue of organization and the fact that I lose things that are loose on their own than it having to be a MAC product.
I think its amazing that people took "disloyal" so seriously in this thread, it seemed extremely obvious to me that she meant it tongue in chic. I suppose there are people out there that take brand loyalty to an extreme, but luckily I've never met any of them.
I don't understand the lipstick and blush comments though I have to say. I'm naturally flushed and for the most part (except for the occasional va-va-voom red) I only like sheer natural colours on my lips. I use MAC lustre lipsticks most of the time, though not exclusively, and the more natural shades for me are just MLBB. For the blushes, I actually HAVE to use MAC as I find that in other brands they are way way too pigmented (such as NARS) and I look like a clown. I like MAC sheertones, and again they melt right into my natural look and are never obvious.
Personally I think that the idea that they are so obvious has more to do with application than the actual product. Sure they do have extremely bright lipsticks and blushes, but I have had a hard time finding colours that suit me in other lines that are sheer and natural enough to replace the more natural lipsticks and blushes they DO have. MAC has a huge colour selection and many different finishes in each product available at any time. Much more so than any other brand I can think of. If you want to find something to hate, its easy, because chances are not only do they cater to the type of look you love, but the type of look you hate as well, no matter who you are.