power user

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun computing A person who makes heavy use of computers, running many applications and doing complex work (as opposed to an ordinary user who tends to just run one application at a time and do simple work).
• noun computing A user of a personal computer who can utilize advanced and complex functions and programs which are outside the reach of normal users
• noun computing A computer user who seeks and uses products having the most features and the fastest performance.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (computing) a computer user who needs the fastest and most powerful computers available