I think perhaps my approach to metering with my in-camera TTL meters is different from the "default." I'm not hoping for a meter that will look at any scene, understand what it is, and spoon feed me the singular perfect exposure every time. Really all I wanted was a camera with a metering area I understand (whether that's full frame, biased towards the bottom, partial, center-weighted average, or spot), that matches my spot meter. And when I say "matches my spot meter" I mean if I fill the entire metering area with an evenly-illuminated, homogeneous subject (a concrete wall on a cloudy day or what have you), then the camera will give me the same recommendation to expose the whole thing at Zone V as my spot meter.
I believe I have achieved this with my favorite two 35mm SLRs (an OM-1 and an FTb) After soldering in diodes to both meter circuits to allow for SR44 batteries, and then using the built-in calibration tools (a brass cam on the galvanometer of the OM-1, and a couple of potentiometers on the FTb), I got excellent and reliable matches (less than 1/4 stop) between the cameras and my spot meter at EV9, EV12, and EV15.
When I actually go out and shoot slide film in my FTb, I'm using its well-defined rectangular "partial" metering area in the center of the frame to check a shadowy area in the foreground, the sky if there is a sky, etc. to get a good idea of the subject brightness range of the scene, and then placing the most important shadow or highlight where I think it ought to go. Not just pointing it somewhere and centering the needle in the lollipop.
The OM-1 is trickier since so far as I can tell, it uses the entire area visible in the viewfinder to get an averaged meter reading, with no bias that I can detect towards the bottom of the frame (such as the bias found in my XA). Often I end up walking closer to an area of shadowy foreground so I can get a meter reading where the entire frame is filled with only shadowy foreground. I can repeat the same exercise by filling the frame with sky, in order to understand scene brightness range, if I intend on including sky in the composition.
Or, basically, I'm using these meters as imprecise spot meters. Imprecise in the sense that it's more difficult to isolate a single area of tone that I want to place on, say, Zone III, but not imprecise in the way that the readings themselves, properly understood, are inaccurate. I believe that the exposures I am choosing for a given scene are the same with my built-in meter as they would be if I happened to use my external spotmeter to make the decisions. That was my goal, and my definition of "perfect metering."
Sometimes, in trickier scenes that have a lot of smaller areas of different brightness, where it's hard to fill the metering area with something I considered a good representation of what I'd want to put on Zone III or Zone IV, I will set my composition, take my best educated guess at what the actual "average" brightness of the entire scene is (perhaps the entire scene, if averaged together into a gray rectangle, would land somewhere around Zone VI instead of Zone V, for example), and expose accordingly.
So far results have been great since I got the metering circuits in these cameras modified and calibrated.