I've never heard that advice about not expecting to be able to piece and FMQ on the same machine. I hate to say it sounds like drivel, but, well, it does. Or maybe I have just been lucky. I haven't found a machine that wasn't fit for piecing, although some may be easier than others because of their bells and whistles. People do FMQ on their Featherweights, although the throat is small.
Is it possible that your 180 needs adjustment? It shouldn't be twisting the fabric. I'm not familiar with the 180, but I have no problem piecing on my 440, and doing FMQ on it too. I found this review of the 180 -
http://lovestoquilt.com/guild.asp?ar...t/000605_a.asp
The reviewer states that the 1/4" foot doesn't work well with the 180, but tells how she was able to get a 1/4" seam using the all purpose foot and needle position #7. She states that the Bernina fed the fabric evenly without a problem.