The DS3 triggers' problem was that they were curved the wrong way. They require you to move your fingers way more to get the same effect, and when fully depressed you'd have to clamp the controller extra hard to maintain your grip on it, which for me lead to cramps after using it for a long time.

I could never play GT5 and 6 with triggers for acceleration/brake because it started getting painful after like 20 minutes. A shame, as it is far easier to apply precise amounts of pressure with those compared to the face buttons.

The gamecube controller had a similar problem with the triggers, but I had no games that required you to keep them depressed for long periods of time on that console.