Impressive... I guess they can be impressive, but not in the sense that big boobs make me think I want mine to be big as well. Quite the opposite really.
I enjoy sports and being physically active and big boobs are like torture devices when you're active. I know several women with large breasts and their boobs cause them nothing but discomfort and pain. They also struggle to find clothes that fit well.
Also... Bras. They're necessary when you have a big chest but dear god, bras are so uncomfortable after some hours, even ones that fit properly, and with big boobs you can't ever go without really.