Sounds more like a very small security risk, to me. For most people if someone steals their laptop it doesn't really matter what kind of RAM is in it.
If you're in some kind of high-security role then use a laptop with volatile RAM instead. Non-volatile will probably be more expensive than the old stuff for quite a while so it's not going anywhere.
Sure, but anyone who's still running WindowsXP on their laptop wants to suffer.
As always, the security-minded will be able to secure their devices and everyone else will not care until it bites them. ULTRARAM isn't revolutionary in that regard.
There's always a tradeoff in computing between security v/s performance/overhead, so the value of it depends on your threat model, and the attack vectors you're expecting.
Anyways, RAM encryption is generally "available" in various forms, depending on the mobo, CPU, software used etc, but it's not commonly enabled/used. Most AMD boards (at least, mid-range and above should) have an option in the BIOS to enable Secure Memory Encryption (SME). This allows the OS to selectively encrypt memory pages, making use of a hardware AES engine that sits outside of the CPU.
There's also Transparent SME (TSME), which encrypts the entire memory and works completely independent of the OS and software. Usually only high-end/workstation boards have this, and it also requires a Ryzen PRO CPU. TSME also has a much lower overhead, I recall reading somewhere it's something like only 5%.
I believe Intel also has something similar, but I never looked into it.