IMO PIxar became a noteworthy brand before Disney even acquired them. For the longest time, there were people who didn't want Disney to acquire them in fear that they'd ruin the brand (instead we can thank JL for his best attempt at that.) I think people forget, but the idea of that annual 'Pixar' film was one that was always buzzed about from moment any info dropped. It was a high mark of quality, each and everytime -- in the same way that there are certain record labels where everyone loves every single band/record they release.
It didn't matter what the film was or what it was about, you just knew it was going to be amazing and sell boatloads of tickets. You knew there was going to be a fun little, but just as memorable and great, short in front of the feature. It was an event and so many people bought their tickets just based on the name Pixar alone.
So to answer your question, in my eyes and the eyes of many, Pixar was a beloved brand very early on and easily distinguishable from Disney, Dreamworks, or any one else doing similar work in the industry.