Hello Boris
Limitations to any technology can be a subjective matter. For one person, one aspect may be limiting while another may not. Compared to NAT, the fact that NPTv6 can only provide a one-to-one translation may be a limitation for someone that wants this functionality, however, NPTv6 was not developed for this purpose. For others, the fact that you can’t have mismatched prefix allocation sizes is a limit.
NPTv6 was developed in order to provide a very simple functionality: rewrite the IPv6 prefix. That’s it. Now for some this is a limitation, for others, this is exactly what they want it to do.
Some things that are limitations, regardless of how it functions or what it’s purpose is, is the fact that IPsec cannot be used across an NPTv6 translation, and a more complex DNS setup is required, specifically, split-horizon DNS must be applied.
I hope this has been helpful!
Laz