Anyone who doubts the importance of aesthetics in the high-end of the mobile phone market should look at the effort invested by Motorola, Sony, Samsung and the rest in differentiating their products. Companies are experimenting with many materials, even wood and leather, to lend their devices some sense of style.
Now style is hard to quantify and achieve because it involves balance, but people seem to recognise it when they see it. There are rules of thumb and examples we can point to, the Lumia 735 come to mind. Despite already owning a 920 and a 930, when I saw the 735, I wanted it and almost bought one when the first Windows 10 TP was released. It was only the fact that the 735 wasn't on the original list of supported devices which stopped me. I still like the idea of owning a 735 and have to stop myself buying one. Anyone who has ever felt desire for something that looks good knows what I'm talking about.
If you look at the designs I bought, the 920 and 930, you see that they are both clean: there are no camera humps and trim is used sparingly. These devices all look as if they are one piece, even when it's clear they aren't. The 920 looks like it's been extruded from a tube, while on the 930 the back cover comes very close to the edge of the device, keeping it clean.
Trim wise, the 920 has a metal strip which surrounds the camera lens and has the branding on it. It is also very slightly raised, helping to protect the lens and body of the device when it's left on a table, but not so much as to distract. On the 930 the metal surround is the only trim on the device. Nokia clearly use the KISS principle: Keep It Simple Stupid.
With the 950/950XL renders there are various things which disturb the simplicity of the design; we've all read complaints regarding the ugliness of the ring on the back of the 950, which aren't raised on the 950XL where ring is modest. The XL also benefits from the flash being integrated into the camera hump, though they have also met with criticism, because they disturb the eye and trip the fingers. What is particularly disappointing here is that with all the noise in the design, they're not particularly thin either. Another disappointment is the paucity of colour, the only thing you can do to make ABS distinctive is colour it. I can see myself buying a spare case and painting it, not easy on ABS if it flexes.
After waiting so long, expectations were high for Cityman/Talkman and previous Lumias have set a precedent these new designs don't seem live up to. I'm going to reserve my final judgement for when I see them, but I can't say I'm confident and having to invest ?500 or more for something so bland doesn't appeal.