Agreed, most plants benefit from liquid carbon, even low-tech ones that don't strictly need it.
There are a few plants that are sensitive to liquid carbon.
Anarcharis is notorious for melting if you use liquid carbon. It sure melted mine really fast, although mine wasn't in the greatest shape to begin with. I've also heard of people having issues using liquid carbon on Vals, and occasionally crypts. That said, I don't have any problems with liquid carbon and my current plants, and I have a few crypt wendtii's.
Even sensitive plants can work with liquid carbon. There are folks out there with Anacharis that dose it have the plants thriving, but they've generally worked on acclimating the plants to it.
If you are concerned, I would start off with light doses, and slowly work your way up. Keep an eye on your plants, particularly the crypts. If anything shows damage, skip a day or two to let them recover some, then drop the dosage down a bit and resume.