I suspect that if you use the HOSTS method which I will try posting a small guide to it might be a slight slow-down. I am unsure if the PC checks against all 1000 entries but I doubt it, I can verify this from a reliable source by next week.

If you use the .reg file and integrate the list into IE it will boost the process.
--Why, well IE immediately checks for a cookie as soon as DNS is resolved and a connection to the remote host is achieved. This is why when you save your local data into a cookie you are always (or so it seems) logged into various websites without ever again being prompted for passwords and nicks. If this is rejected the website loads, if a cookie is accepted, it must be verified, its contents might be updated if need be, and if it is a spyware cookie an exchange of information occurs. This takes much more time than an immediate rejection of the cookie, because more happens in the process.

There seems to be the impression that all entries are checked against before a block is made. This would of course imply a slowdown. However, this is not the case I assure you. By no means can this possibly slow you down. Some meber here already see this. try it on dial up and you will really see a difference, just by the ads blocked alone

Hope that clears it up some.