I seem to have mellowed a tiny bit over the succeeding decades. In 2016 I posted "What Were They Thinking?: Jaguar XK150" and concluded, stating:
"From the perspective of nearly 60 after its announcement, the XK150 doesn't irk me as much as it did when new. Much of that has to do with the fact that the 120 has also receded from view (they're seldom seen on streets and roads these days) dulling my sense of comparison. That said, the 150 is not a good design. Bulky, with awkward detailing. William Lyons surely abandoned his good taste with this one."
In 2019 I compared one aspect of Jaguar XK series designs in my post "Jaguar XK120 to 150 Fixed Head Coupe Evolution."
The present post features a walkaround of an XK150 Fixed Head Coupe, photos via Bonhams Auctions.
I'm avoiding comparisons with earlier XKs, attempting to evaluate the XK150 design in isolation (though that's not necessarily an easy task, given my youthful imprinting by the classic XK120).
The frontal aspect is classical, working well with one exception. Even though there are many rounded features on the lower body, I find the top windshield framing (and the roof behind it) slightly too curved.
The cowling seems too high. Perhaps there were engineering reasons for that. Otherwise, the hood could profitably been lowered and inch or two (25.4-50.8 mm). And made less rounded, along with the lower windshield framing.
The fenderline seems to sag in the middle. Its rear fender zone looks odd because its peak is well aft of the wheel opening. Ideally, the high point should be aligned with the wheel's hub. The door's aft cutline and related metal stamping structure made a rising curve starting at that point potentially a little awkward. A rise beginning on the door would interfere with the door handle, so there was no easy solution given the existing front fender design. Still, a differently centered rear fender profile is needed.
The backlight window is too wide because the C-pillar looks too narrow.
As noted, a flatter, less-curved roof would be an improvement. There are too many curves, roundings, on this design. A touch of contrast would improve things.
A flatter, somewhat more angular passenger compartment greenhouse could yield a wider C-pillar and a more squared-off after side window. That, along with a lower, flatter hood would improve matters. So would a more curvaceous fenderline.
But the frontal aspect could be retained.