Might depend on the type of boots and if the jeans are completely tucked in (showing the entire boot). I think that if a guy is wearing "cowboy boots" and tucks his jeans in completely and walks down the streets of NY, he is looking a bit too bold for my taste. Possibly, if he lives in Texas... If a construction worker is working in Manhattan and has his jeans tucked into "work boots", and the jeans have a bit of a rolled over effect I think it is OK. If it is snowing, and a businessman is wearing snow boots with his dress pants tucked in, that is acceptable (as long as he plans to change into his dress shoes when he reaches the office). Anyway, my first instinct is not to tuck in the jeans.. However, depends on the situation and or fashion statement.