It's worth it if you actually push your XV Crosstrek to its limits during cornering, wish for improved chassis response, and still desire good ride quality. Otherwise, if you simply drive like the average American driver, it's just dead weight.
I have a solid bar, a Cusco front strut tower brace. Although I didn't initially feel a big difference, I had my brothers drive my car before and after, and they could definitely feel a difference in the chassis. And through some long-term driving, I've realized that the solid strut tower braces do actually make a tiny little difference in ride quality, as pothole-ridden California interstate freeways have shown me.
Now, I should clarify that all these chassis bracing are not the kind of mods that have the best "bang for your buck".
In short, chassis bracing will not deliver significant enough "feel" in improvement to justify the costs for most drivers. If you drive hard on and off-road, it may be a good idea, but if you never ever take your XV to 100% whether in the twisty mountain roads or rutted off-road trails, you are better off looking for a different kind of modification.
If you do feel that a brace is worth getting, I would actually recommend the STI Flexible Strut Tower Brace over a solid Cusco or SSD brace, which may slightly add harshness to the ride quality, for a daily-driven commute application.