I would be interested in hearing from anyone who has tried Ink Scape about the pros and cons of using this program.
I have a few thousand files
That is actually one of the alternatives that I use (there are only a handful of ones that are available on Linux (my platform of choice) and a lot of them not many have heard of).
It's native format is SVG (although it will read the legacy ai and eps formats and I think there is some support for CDR as well). The thing to keep in mind is that SVG, while an open format, it is mainly geared for the web. Which also means that it is also simple text (XML is simple markup) in a regular text editor (notepad, neovim, VSCodium etc).
The biggest advantage is if you know Python (which isn't that hard relatively as far as languages go and I have dealt with a lot of compiled and scripting language and it is easy to pick up), you can pretty much extend it to your harts desire (the last embroidery software that I ran after dealing with the $15k versions is a plugin for Inkscape (the official embroidery plugin done by a commercial company for Ai and DRAW was $3k in price and it had some features, but didn't have one feature that I specifically needed (although I am in a small minority of users of that feature in the US, Japan (or Asia in general) is another story)). Now some people consider these plugins are hacks, technically they are correct, but the irony is
all plugins are hacks. I just find it ironic they will call plugins for these types of programs hacks, but plugins for Ai and Draw get listed as plugins, when technically they are all hacks (like it or not, the term "hacks" comes with negative connotations, and not always deserved at that).
Now, something to keep in mind (and this is a con with Ai and Draw) is that with Inkscape and especially with plugins like the embroidery plugin, info is stored in the SVG markup. Inkscape will ignore markup that it doesn't know or isn't HTML5 kosher markup. Ai and Draw will delete that info on save. So if using a plugin that stores object info in the XML (which they all do is the main format is SVG which is markup) and try to edit it in Ai or Draw and save it in those programs, that plugin info will be lost and need to be re applied. I find this ironic, considering if you were to do ePub export from InDesign for example, the exporting HTML file (which ePub, for those that don't know is a zip file (can change the extension to zip and it will open) with HTML5 files (mainly your assets, html and css files, newer versions of ePub allow for JS, but not all readers accept that yet)) is not able to to be edited on it's own, nor is it the recommended way to handle HTML/CSS in a modular maintainable way (atleast not from what I have seen, it may have, but I'm not holding my breath on it). So they have ignored kosher HTML spec on exports of their own as well. At least as far as I'm concerned, because I do like to do edits with the export because it is far quicker to do that with the export compared to the master file itself (usually because it is specific to ePub and not necessarily to InDesign, but I digress big time).
There are quite a bit of extra functionality with using the built in Inkscape XML editor to enjoy more features (particularly in relation to some extra font features and for even greater precision of the existing tools).
You do not need to write XML from scratch to enjoy these features. Just select the object (text or shape) open the XML Editor portion of Inkscape and edit the TextEdit or SpinBoxes accordingly for that object(not any different compared to those same widgets in Ai or Draw for editing their individual vector objects). It is based on HTML5 specs (or W3 specs rather), so not everything is still viable versus Ai/Draw options because their native format is their own format (so that can be a con for Inkscape), but it does give extra options compared to just the regular tool(s). Rather or not that is good UX is something else, but just to keep in mind that does help with some extra functionality.
Oddly enough, Blender actually has SVG support as well. Can create it for export (Blender 3.0 and later if I recall correctly for this support) using the Grease Pencil tool (Blender's 2D toolset) and import as well if the extension (which should be shipped with Blender, just not on). I have actually used Blender for more and more 2D work (animation and SVG work), but not much for game asset creation, that I use Krita for (mainly do to it's DPI rendering for pixel exporting). But I would only suggest Blender if you are familiar with Blender's way of doing things, otherwise, stick with Inkscape. I just thought it was a cool alternative to mention as I really do like Blender.
The others you wouldn't have heard of and they are typically either web based (hosted locally and doesn't send anything to servers) or they are Linux only.
Two big cons, and one is a personal preference, SVG is mainly a web-standard, as such, options are typically limited to what the web can handle. That is getting better all the time and it might be sufficient for what you need right now, just something to keep in mind as that determines what you can/can't do and how you can do it at that. Also, and this is the preference one, I am not a fan of GTK widgets. I think the UI is ugly. I'm a "cute" fan not a Gnome/GTK fan. Which is also a reason why I use Blender as much as I can for SVG work. I don't mind the Immediate Mode gui (some do, I don't and that's the way things are going anyway, I'll either use SDL or Web Rendering for my own apps as well, quickness depends on which one I use).
What I would try to do to help with the learning curve, is keep Draw around for your customer work right now, and when you are creating your own work, start using Inkscape. Nothing helps cement things and makes me learn things compared to having a project to do (and that applies to just about anything that I am trying to learn, but that is me, may not be you, just depends, just suggesting what works for me), but while X8 is still good, have that to fall back on while you are learning the ropes (and see if it is a true replacement). Thing to watch out for is if X8 doesn't become too much of a crutch and prevents one from learning. That is the dangers with that as well. Always something, but it really is going to come done to what you need from your software and how willing you are to learning a different way of doing things (people sometimes confuse a different way of doing things with a software lacking functionality that they need).