As a web developer and someone who programs in a superset of HyperCard (LiveCode) - I must say it was moderately difficult to grasp in the beginning. Strangely enough things that are required for your day job tend to have a way of getting learned. The hardest part for me was not the syntax, but the fact the IDE and the language are so inter-connected.

It's actually a fairly quick way of prototyping mobile apps for iOS/Android - which is one of the main things I use it for at work. Though, I am probably incredibly biased.

They recently(2012) open sourced the IDE, http://LiveCode.com

Actually I still found it easier than Lingo, I wrote a bunch of things while in art school in the 90s but when java applets took off I wound up abandoning hypercard for java.