It is very worth it for sketching. Once you get used to a tablet, it is pretty much like drawing on pen and paper. It feels amazing.
In the past I used to draw on paper, scan it in, and then colour and ink it digitally. With a tablet I simply draw everything from scratch to finished product using the computer.
Oh ... well as a vector software it's not as powerful as Illustrator. The worst part is that it can't save in .svg. However that's not where its strength lies.
Do you use a stylus? Clip Studio is mostly useful with a stylus because it's just about my favourite sketching and colouring tool.
I'll send you a link to one video I used to learn a bit.
I'm still learning the ropes. Any tips or techniques you can suggest for me to try out? I tried running Jill and Alexis through it and... it didn't end very well I'm afraid.