Looking at the comment section you are worried about a sort of vendor lock-in - having your data in a format that nothing else can work with and getting problems when an update messes up your data or the company goes bancrupt, leaving you with useless files that nobody can decipher, which means a lot of lost productivity.
While I haven't used the tools themselves there are quite a few reviews on the internet that can help you get a feeling for how the individual tools work or don't work. It's important to look at them to see if the tools really do what you specifically need.
For example you can find a review of StoryMill under the title Mariner Software StoryMill Review on wine-reviews.com. It's a bit older, but there's an important remark that you should keep in mind when thinking about buying bundles of software:
'll be honest: Contour is not something I'll try because I am not the type of writer who outlines in any detail whatsoever. I have a general idea, pit stops along the way, and an endgame; however, my characters direct me better than any outline I've ever done.
Do you really need all of these tools?
But anyway, the thing I can talk about best is the aforementioned vendor lock-in because that's objectively answerable.
I found a review named Review: Persona is limited, values stereotypes over substance on macworld.com. The title already mentions the basic information you will find: apparently Persona has a lot of information about stereotypes and not much more. But here is the really interesting part (emphasis by me):
At best, Persona is a set of training wheels for writers looking to cut their teeth, but you can find much better sources of information on archetypes and writing elsewhere online or at your local library. Those who already have some experience may appreciate the character logging features, but since there’s no way to get information out of the app, you might regret locking yourself in to a proprietary program.
Moreover, at $50, Persona strikes me as simply too expensive for its limited functionality. It’s a lot to pay for an app that, if all goes well, you will outgrow pretty quickly.
That means the character data will be stuck in Persona. There is no way to get it out of there. Be careful if you really want to be locked in.
On the same site you can also finds lots of more useful reviews, like Mariner Write 3.5 and Mariner Calc 5.2 (emphasis by me):
As stand-alone programs that provide the features most users actually need, without the powerful (and expensive) features in Microsoft Word and Excel, both Mariner Write 3.5 and Mariner Calc 5.2 perform perfectly. They can ably handle most day-to-day word processing and spreadsheet tasks. But when viewed from the perspective of interoperability with Word and Excel, Write and Calc are overshadowed by the more feature-rich and considerably less expensive AppleWorks.
But be aware that this review is very, very old - 15 years...
For Contour you only find an old review for an older version from 2009 Contour 1.1, which looks like the software was at that point pretty good for its usecase. The same for Montage.
Narrator, according to the developers,
also [has] an export option for ACC sound files to use with other sound playing software such as a soundtrack in iMovie or as a screenshot voiceover.
All in all there is not much to be found out about the software. I haven't used it, but it seems to be directed more at beginners than experts and there don't seem to be many export options available. Most tool descriptions don't mention something along those lines. Whether the software would be helpful to you is up to you, but you should definitely thoroughly check each one before deciding whether you want to purchase. Especially when buying a bundle you should also check whether you really need all of the software. Not every part of the bundle may be for everyone. An important part that should not be forgotten is that the software apparently has been around for quite some time - that means that there is an active enough userbase that it's still possible for the company to further develop their tools. That's alwas a good sign and suggests that you probably won't have the problem of the company disappearing over night and leaving you with a bunch of completely useless files. Probably...
On the other hand here is a review for a different product from them: Paperless. The users there are complaining about the software frequently hanging whle trying to quit it, horrible tech support.
So if you are reading this because the feature list on their website didn't convince you that the tool would be perfect for you then you might want to stay away from it for the time being. It doesn't seem to be so exceptionally good for writers that everyone's going to them and the price is quite high when you really need all of their software.