A B737-300 CREW; DEPARTING SLC; TOOK OFF WITH THE RPTED WX BEING BELOW THEIR COMPANY'S TKOF MINIMUMS.

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I CONFIRMED DEICE PROCS WITH STATION PERSONNEL; AND THEN ARRIVED AT FLT DECK; WHERE FO ADVISED OF 2 MAINT ITEMS THAT NEEDED ADDRESSING PER MEL PROCS. AFTER PUSHBACK FROM THE S SIDE OF TERMINAL; WE TAXIED S TO DEICE AREA. COMPLETED DEICE FOR FROST; THEN TAXIED SBOUND TO RWY 34R. NOW COMES MY BREAKDOWN IN APPLYING JUDGEMENT AND SOUND THINKING. UP TILL NOW; WE HAD SEEN NOTHING BUT GOOD VISIBILITY (1+ MI) WHILE PROCEEDING SBOUND. I WAS STILL CONCERNED WITH DEICE HOLD OVER TIMES WHILE TAXIING AND IT DID NOT REGISTER IN MY MIND WHEN GND CTL MENTIONED RVR 5000 FT TOUCHDOWN; 400 FT MIDFIELD; 300 FT ROLLOUT. THE LAST 2 ARE BELOW MINIMUMS FOR OUR OPS SPECS. I ASKED FO; 'ARE WE OK ON VISIBILITY?' HE ADVISED 'YES; BETTER THAN 5000 FT RVR.' HE WAS WRONG; I WAS WRONG; WE TOOK OFF. CONTRIBUTING FACTORS: 1) COORDINATING SECURITY BRIEFING; DEICE PROCS; MAINT MEL'S ALL AFTER ARRIVING AT ACFT. 2) ON THE S SIDE OF TERMINAL AND TAXIING S; WE NEVER SAW ANY FOG OR LOW VISIBILITY. 3) HASTE TO DEPART WITHIN HOLDOVER TIME FOR DEICE. 4) DEPENDING ON FO RPT OF TKOF VISIBILITY WITHOUT DOUBLECHKING MYSELF TO CATCH ERROR. 5) IRONICALLY; WE HAD ROTATED AND BECOMING AIRBORNE BEFORE SEEING THE GND FOG ON THE RWY. 6) NOT FULLY PROCESSING MENTALLY ATC RPT OF RVR. CLASSIC CASE OF HUMAN FACTORS IN TRYING TO DO TOO MANY THINGS AT ONCE AND NOT FULLY USING ALL INFO RESOURCE AVAILABLE. YOU CAN BET I'VE LEARNED A VALUABLE LESSON! SUPPLEMENTAL INFO FROM ACN 538289: HOWEVER; WE DEPARTED FOR TKOF BASED ON THE RVR'S OF 6000 FT; 500 FT; 400 FT. WE DISCUSSED AND DECIDED THAT IN ORDER TO HAVE TO USE THE 3 RVR'S THE RVR FOR TOUCHDOWN WOULD HAVE HAD TO BE LESS THAN 1600 FT RVR FOR TOUCHDOWN. WE THINK WE DEPARTED LEGALLY OF RWY 34R BASED ON THE RVR'S BUT ARE NOT POSITIVELY SURE.