AN MLG ACR CREW; WITH ALL OF THE BELLS AND WHISTLES; HAD THEIR AUTOPLT COMMAND A COURSE AND ALTDEV.

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ACFT WAS NW OF CVG AT 12000. 12000 WAS SET IN THE ALT ALERT WINDOW. CAPT CREATED A NEW WAYPOINT 35 NW OF CVG AT 12000. AS ACFT PASSED SHB; IT CONTINUED A L TURN PAST COURSE AND BEGAN AN UNCOMMANDED CLB OF 10000 FPM. ALT PASSED APPROX 12700 WHEN AUTOPLT WAS DISENGAGED AND ACFT RETURNED TO 12000. UPON REACHING 12000 AUTOPLT WAS REENGAGED AND FUNCTIONED NORMALLY. SUPPLEMENTAL INFO FROM ACN 217250. FO OBTAINED ATIS AND SELECTED ILS 18R FROM DEP/ARR OPTIONS IN DATA BASE. HE POINTED OUT A 'GLITCH' IN THE PROGRAM THAT CAUSED COURSE LINES FROM A POINT BEHIND THE ACFT TO ADDYS (LOM FOR ILS 18R AT CVG) THAT THEN RETURNED TO ANOTHER POINT; ALSO BEHIND THE ACFT. THE FLT WAS CLRED TO CROSS 35 NM NW OF CVG AT 12000. FO SET 12000 IN THE ALT ALERT SYS. I CREATED A WAYPOINT 35 NM NW OF CVG (CVG01) AND INSERTED 12000 AS THE ALT FOR THAT WAYPOINT. THE AUTOPLT COMMANDED A TURN THAT PASSED THROUGH THE COURSE FOR CVG01. I IMMEDIATELY DESELECTED THE LNAV MODE; SELECTED HDG SELECT MODE AND INITIATED A R TURN TO BRING THE ACFT BACK TO 'ON COURSE'. DURING THE LATTER PORTION OF THE TURN; I NOTED THAT THE ACFT WAS IN A VERY SMOOTHLY ENTERED; AUTOPLT COMMANDED CLB OF APPROX 1000 FPM; PASSING THROUGH 17000 FT. (NO ALT WARNING AVAILABLE AS THE ALT ALERT SYS WAS SET TO THE NEXT CLRED ALT). I DISENGAGED THE AUTOPLT; INITIATED AN IMMEDIATE DSCNT; CONTINUING SAID DSCNT TO THE CLRED ALT OF 12000. UPON REACHING THE LEVEL-OFF ALT; I REENGAGED THE AUTOPLT AND IT FUNCTIONED NORMALLY UNTIL DISENGAGEMENT ON THE ILS FINAL COURSE. AN AUTOFLT SYS CAN BE A GREAT FUEL/LABOR SAVING DEVICE; BUT I HAVE LEARNED THAT THE SYS PERFORMANCE MUST BE MONITORED VERY CLOSELY.