Hi, I don't know if there's any solution to this, but it's worth a try.
Last night I upgraded an intranet (hence can't give URL, sorry) to the latest version of WP, v 2.0.4. I cut down on the plugins I've been using for the last three versions, but my site is now running like a snail on tranquilisers.
I've dropped some redundant SQL database tables, I've optimised the SQL database, and I've disabled plugins which aren't strictly necessary to the functioning of my site. I'm using a very plain theme with no graphics which I haven't changed for a long time, so I doubt it's that which is causing the problem. I've even installed a WP-Cache plugin, which seems to be helping a little, but not enough.
I'm really loath to get rid of any plugins as I figure I really need the ones I've got - they've worked fine with all the older versions of WP I've used so far.
Can anyone suggest anything else I can do to speed things up other than disabling plugins? I'd love to hear any ideas because this lag in speed is driving me nuts!