The first and most important thing to keep in mind:
THIS TEST WAS NOT DESIGNED TO EXCLUDE PEOPLE FROM GETTING A TEXAS CHL.
This test was fully and intentionally designed so that anyone that can safely handle a firearm can pass the test.
More than a full third of your score comes from firing at a target 3 yards away. At that distance, you can almost reach out and touch the target with the muzzle of your weapon.
My personal experience:
I had known there was an actual shooting test for the CHL, but the only handguns I had at my disposal at that time were a .38 Spl Taurus revolver, and a Raven MP25. The Raven doesn't meet the minimum caliber requirement, and the revolver only gives you a revolver permit. I asked the instructor if I could borrow one of his pistols (he brings a briefcase full of 'em just for that purpose), and he handed me a double stack .45 Para Ordnance 1911.
I had never handled one of those before. I hope I never have to use one in defense of life and limb. The grip was uncomfortable, and I did not bring shooting gloves (I could've sworn they were in the gym bag along with my shooting glasses and earmuffs, but they weren't!). Worse than that, it was the beginning of January and the wind was blowing. I was rapidly losing sensation in my fingertips by the time he got the targets set up downrange.
After the first 10 shots, I had developed a flinch, from being unused to the grip, and the recoil of the gun. Halfway through the second portion of test, I could no longer feel my trigger finger from the cold and the wind.
Around the beginning of the 3rd portion of the test, I could feel my denim jacket losing its effectiveness, and I was beginning to shiver a little.
My final score was still over 275
Edit: I was meaning to type '175', as in the minimum score. Can't believe I didn't notice the typo until now.