A reader wonders whether to take a one-year non-tenure-track teaching position that seems like it might become a tenure-track opportunity after a year or wait and apply for the TT position, should it come into existence. In this case, the institution in question is a teaching-focused university, with some (but not major) research expectations for faculty.
The underlying question is whether being the temporary person gives you the inside track (if they like you) or whether you would spend the entire year making newbie teaching mistakes and thereby damaging your chances of being considered for the TT position. Would colleagues be likely to say "Hey, look how hard s/he has been working! Wouldn't it be great to have him/her as a colleague?" or would they be more likely to say "Hey, we know this person and they seem to have some imperfections. Let's try to hire one of these shiny new perfect people whose applications clearly demonstrate -- particularly in the letters of references -- that they have absolutely no flaws whatsoever!"
My personal experiences with this are mostly from my early days; i.e., as an applicant and visiting professor. I don't have any experience with it as a professor making decisions about hiring; for various reasons involving how my department works, we seldom have people in this position. It is also rare that postdocs become TT professors here, so I can't discuss a possibly analogy from personal experience either.
In ancient times, when I was on the job market, I interviewed at two places that already had 'visiting professors' who were candidates for the tenure-track job. The first time it happened, I figured I would just get some experience interviewing, but couldn't imagine why they would want to hire me instead of keeping someone who had been there for several years and had a lot more teaching experience than I did. I was quite relaxed during the interview because I was so sure it wasn't a 'real' interview, and was therefore shocked when I was offered the job. I didn't end up accepting that offer, but I remember feeling apologetic when I later saw the person who was passed over for the TT job. Fortunately, this person ended up with a good TT job at another institution. I think in that case, it was a situation of a department's favoring of the unknown over the known, and not necessarily for any good reason.
Then it happened again, not long after that experience. I went to an interview for a tenure-track position, again convinced that it was the 'visiting professor's' job, and this time I was right. This time, I was told directly by more than one person that this was X's job, and the interviews were pointless. One professor, scheduled to talk to me for half an hour, told me that I was wasting his time. It didn't occur to him that he and all his colleagues were wasting my time, but whatever. It was an unpleasant experience to be told directly (and often) that there was no chance I would be hired. Thanks for the free trip to Unpleasant City! So they hired X, who did not ultimately get tenure. I could gloat about that, but I happen to like X very much.
Another time, I was the visiting professor, but there was no chance of this job becoming tenure-track, so I didn't get to run the experiment with me as the known being compared with shiny new unknowns. In that case, I took the job because I wanted the teaching experience (this turned out to be very useful, even in my first TT job at a research university) and because I thought I wanted to be at a small liberal arts college (I was wrong).
So, those are my experiences. I'm not sure if they add up to anything coherent in terms of answering this question because I think they show how variable these situations can be. It's hard to predict whether your colleagues are going to appreciate your hard work or whether they are going to have a 'grass is greener' view of applicants for the tenure-track position.
Nevertheless, even if you don't end up getting the TT job, I think the experience can be very useful. If your life is such that you are mobile enough to take a short-term job (or two), you can make all sorts of newbie mistakes (ideally not so bad that your students suffer for it..) and then if you do get a TT job, you will be awesomely prepared and ready to roll, at least in terms of teaching. You can also check out a certain type of institution (as I did at a SLAC) and see if that is a good fit for you, and you can see if your colleagues are people you'd want to work with long-term or whether you want to run screaming away from that place as soon as you are able.
So, if a short-term job is at all possible for you and even somewhat appealing (relative to other options), I say go for it. Check the place out, check the people out, get some teaching experience, and get some visibility.
IMPORTANT NOTES: In my field of the physical sciences, these short-term positions do tend to lead to real jobs. They do not tend to be low-wage, low-respect, dead-end positions. Most people do not bounce around in these visiting positions for long periods of time. These positions are a respected, accepted way to get some experience that is a bit different from what you get in a postdoc. The person who wrote to me is in my field.