In reply to simmcc:
Depends to some extent when you're going. You may find plastic boots are overkill and you can survive with some robust general / B2 mountaineering boots. When we went to IP in April one of my companions climbed in (rather heavy) Salomon Mountain Experts and the other got by in stiff, well dubbed, leather walking boots.
I would suggest that the priority is to make sure the boots you have fit and are broken in before you go and make sure you look after your feet on the trek up from Lukla. As simmcc says, you're not high for all that long.