I think everyone "looks". There are a lot of attractive people out there. However I think a lot of people get jealous too. In some way being open about it... at least you're... well, being open about it and not hiding and looking behind your partners back. On the other hand, mentioning it... if they get jealous, well, they get jealous and then might think 'so? I don't want to know who you fancy' or maybe just worry 'are they hotter than me?' but it's all insecurity really. As long as your partner WON'T go off with said attractive person, I guess it doesn't matter. I imagine, though, that it would be somewhat easeir if both people can "look" and say 'yeah, that person is hot' but also know that said person isn't hotter than your partner and you won't be running off.
To be fair, I'm my namesake on here (lustful) and I can be quite visual etc, SO... yeah I've always "looked" at hot people. As I say though, and this is really how I feel, I have not seen anyone I find MORE attractive than my boyfriend now. Not even famous people (although people like Noel Fielding and Jake Gyllenhaal could be AS hot, I suppose!).
I do get a bit jealous if my guy "looks" but then, that's just human nature. Although if we both found the person attractive, it could be easier as I say, 'cause then I could at least see where he's coming from, or vice versa.