Welcome to WebmasterWorld, troi21!
The most important site currently supplied by Inktomi (at least in US) is MSN.
Nobody knows when Yahoo will switch.
Inclusion will not give your ranking a boost. Also note that you have to pay for each page that you want included, they do not spider your whole site for the price of just including the index page!
There have been many suggestions, in fact, that once you start paying for some pages they may drop other, unpaid, pages from the index.
Their current model is a strange (in my opinion!) hybrid: They spider any page that pays for that privilege (but with no guarantee at all as to where it will rank), and at the same time they spider the whole web for pages they consider "important" (not sure what ther criteria are, probably links count).
For some time I have had all my pages indexed for free, so obviously I have no interest in paying!