no, they're terrible. Not only do they lead to extremely messy code, that code is also impossible to maintain by people who are not Java programmers. JSP are meant for maintenance by website authors.
You can do everything you can with scriptlets by using custom tags, and much of what you can do with scriptlets you shouldn't be doing in the first place (like anything that's not purely presentation logic).
Surely when it comes to say looping/ organising presenting data they're great
People thought the same, at first. Because you can do anything. Anything from good things to bad things, especially bad ones for those who did not use scriptlets properly. I've seen jsp files full of scriptlet. A mess it is. Unreadable. From now on, keep it clean, with tags. There are great too.