I generally use trade paints. I find the extra benefit in ease of application and quality of finish amply compensate for their extra cost. The exception is gloss paint. I just cannot get to grips with full gloss, especially around vertical mouldings etc. so I have always used non-drip. And the trade doesn't use non-drip so I'm stuck with inferior retail products.
In the last 20 years the quality of non-drip gloss seems to have been falling further. The last batch I used (white Dulux) was truly awful. It has a very high shine but there seems to be so little pigment it is almost transparent. Even painted over a smooth white undercoat the finished effect is grey and streaky. I am guessing the paint companies are adding more plastic at the expense of pigment.
Are there any really good quality non-drip glosses available?