Strong LL/SC provides the ability to do real software transactional memory. I believe ARM has the strongest LL/SC implementation, with the architecture supporting transaction blocks up to 2KB in size! Although ARM has specified LL/SC such that vendors can choose to only support blocks much smaller than 2KB.
Note that people have totally confused the terms. Originally "software transactional memory" meant using primitives like [strong] LL/SC to get lock-free, wait-free algorithms. Strong LL/SC has been proven to be a universal primitive which can be used to implement most known lock-free, wait-free algorithms.
"Hardware transactional memory" gave you access to lock-free, wait-free algorithms in a much more convenient manner. But really it's a difference of degree because strong LL/SC requires _significant_ hardware support.
These days people (like the PyPy project and most STM libraries) use "software transactional memory" for implementations which just use a mutex under the hood. It's emulated STM; they're just being fanciful.
I believe TSX is more like strong LL/SC. Maybe stronger. OTOH I'm not sure if it's universal enough to implement wait-free algorithms.
So N years more till we see software transactional memory with dedicated hardware support.