Great answers and comments so far, but one thing I would say, which probably will have no effect on search performance, is you should seriously consider moving some of those evals from the search to calculated fields. This is more about knowledge management than performance.
Maybe some of those fields are specific only to the report you are running, but I promise you one day your colleagues will want to use the same evals you have come up with in that search. Give them a head start and don't make them figure out "IO Total" or "CPU/Ready Wait".
http://docs.splunk.com/Documentation/Splunk/5.0.3/Knowledge/definecalcfields
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