I got the bundle a wee while back during its first Humblebundle run, it's a heck of a bargain when you see the full price of Painter normally
How useful the software is kinda depends on what you'd like to make and whether you're prepared to pay for it. I use art programs all the time so if something makes my work more enjoyable or easier then I'll absolutely pay for it. Or donate to OS because I know that's helping make new features I'll get the use of.
The best option is to look at the Corel website and just see if the software features appeal to you. As with traditional media, you get different art programs and it's fun combining them to make something unique that nobody else does. Or you might want to stick with just one tool and use that for everything. I like the variety because I get bored really easily and I like the challenge of mastering new tools and combining them.
As a rough guide, Corel Painter simulates traditional art materials so it's useful if you want a traditional media appearance in digital art. Krita is free/open source but simulates natural media differently. As do other paint programs like Paintstorm Studio, Medibang Paint, Clip Paint Studio etc. Some are geared up for specific work like manga/comic art and have different aids/comic panel templates to suit those purposes. It boils down to the sort of work you're doing and what look you want it to have when you're finished. Or how much you geek out on learning new art programs!
For my more representational style the goal is to put a piece of my traditional art alongside a digital picture and it's obvious I made both and they share the texture and imperfection of traditional ink/paint. Or I scan traditional inking/pencils, colour it digitally and it's nearly indistinguishable from how I'd actually paint it when the brushes simulate real media nicely. If you really prefer perfect digital lines then Painter probably isn't for you. For me it's ideal. I still use Krita and Paintstorm, but for situations where I want the look of their brushes. Say for a more simplified or stylised illustration or cartoons. They can simulate traditional media really well, some brushes are amazing. It's just that Painter takes the simulation that extra bit further when I want that particular look.
Other applications are useful if you need to open/save specific "industry standard" files and output say CMYK. Those aren't always covered by open source packages. If you're only making art for display say on a website or for SL textures, that's obviously less of a concern. In my case I don't use Adobe software but I'm still expected to have those capabilities so I run other open source and paid software and use whatever tool/combo is best for the job. I haven't fully explored the Corel suite to compare it to the other programs I have, but only because I have the full Affinity suite and the full compliment of OS software already. I love collecting design software, but it takes time to learn to use each program fully and I just haven't gotten round to the other Corel goodies. All I can say is look at the info on their website and the videos and you'll see if there's anything you want to use. They will likely have demo versions of everything too, I'm fairly sure I saw links to those.
www.humblebundle.com
