The Imitation of Christ warns the monk not to let his personal devotions be kept to yourself. Of course, if you have a devotion that you engage in in chapel, how can others not see it? Are you supposed to hide your scapular?
In our day that has been taken to new heights. No personal acts of devotion should ever be seen by anyone ever, nor should you ever promote a devotion. Everyone has their own way of relating to the Lord.
What I've notice, though, is that some people who have one form of devotion that they consider "adult" (as in "We need to have an adult faith") look down on others who have a different form as childish, superstitions, or overly sentimental. It seems to me that this attitude has two sources: an over-spiritualization of the faith and spiritual pride. For some, a relationship with faith is purely interior. Those who engage their body during devotions are "carnal" (although they may not use that word). I think the theology of the body has addressed that.
As for pride, what if some people approach Our Lord and the saints like a child? What if they are devoted to images that don't have the greatest artistic value and that seem to us to be overly sentimental. I'd rather think, "I'm glad they have a relationship with the Lord; it is undoubtedly deeper and richer than my own."