I like the flexibility they provide, but it might take more time to get set up than using something like Bootstrap. It depends on your needs. If you build a ton of little projects than Bootstrap might be better. If you build something for more long-term than rolling your own solution is probably better.
For WIP I took the approach of building my custom CSS components and reusing the hell out of them even though that meant the design was pretty bland. Over time I iterated the design so not every single element looked the same anymore. That worked really well for me.
I build my own using Neat and Bourbon.
I like the flexibility they provide, but it might take more time to get set up than using something like Bootstrap. It depends on your needs. If you build a ton of little projects than Bootstrap might be better. If you build something for more long-term than rolling your own solution is probably better.
For WIP I took the approach of building my custom CSS components and reusing the hell out of them even though that meant the design was pretty bland. Over time I iterated the design so not every single element looked the same anymore. That worked really well for me.