Sorry, I don't want a heated discussion. Yes, I have a SL66SE with a set of lenses. For hanheld, I prefer by far my Rolleiflex TLR: you can shoot at 1/30 or less without problem. In fact, one of my work in progress about Spanish gypsies nowadays, is becoming with my 1962 year old Rolleiflex. I enlarge to 20x24" with an outstanding sharpness and quality (I develop my 120 film in a pyro developer of my own).
What do you have theoretically superior in a SL66 on tripod? In fact, the possibility of macro photography and tilting.
But you don't have the freedom of movements of a large format camera... you can't make a full Scheimpflug with SL66 and consequently YOU DON'T WORK with the better apertures of each lens. To achieve an "in focus from 0 to infinity" (very easy in an LF camera using the Scheimpflug technique) you will have to stop down your lens with inherents flare' problems and lost of REAL SHARPNESS. And more: to maintain your lens aperture you will have a elongated exposition with inherents problems like wind, reciprocity failure or others...
But, there's the subjective point of view: if you feel you are ok with the SL66 use it. In fact there are good photographers like the late Diane Arbus they only feel comfortable working with uncomfortable equipment, helas!!!
By the way, do you have see the Hassy 205? I think is a great medium format camera with an oustanding TTL system and the new series os Zeiss lenses are superb.
I have checked the TTL of this camera with my calibrated SpotMeter on a light controlled 18% Kodak Grey Card. The linearity is near perfection would be highlight or lowlight, and as a zone system practitioner for more than thirty years I find the possibilities of this camera are not for ignoring.
If you like the SL66 buy one, you will have a good camera with a very good lens. Additionally you will be able to make some small tiltings that can help you. But please, don't trust the TTL at all and be carefull don't spoil it or your wallet will understand the consequences.
In fact, we have in Spain a sentence: "apprentice of many works, master of any".