I'm a bit a devotee to 20mm tyres, and used them for years, but I'll never use one on the front again; the high pressure isn't necessary on the front, they're just too uncomfortable, and a little dangerous. I finally accepted to science

What used to bug me about 23s was the low psi ratings (often around 115), but then I found a few brands that are rated over 140, just in case a find a glassy road. I'm about 85kg (187lbs), so I find that a rear 23 at 115psi just gets squished flat. Therefore, sometimes I have a 20mm on the rear (at 150psi) just to stop the rim hitting the road.