Its a nice kit. In 1/72 its better than the older Hobbycraft version, although that kit is okay itself.
The Tamiya kit was not tooled by Tamya but is another brand kit in their box. There is/was a small Japanese company that tooled up three or four kits that were sold by Tamiya and Hasegawa. The X-1 was sold by Tamiya... Hasegawa sold the Flapjack and Suishi Japanese version of the Komet. Generally nice little kits. The Tamiya X-1 has a clear fusilage option to show off the interior.
FWIW the Eduard 1/48 X-1 is pretty nice as well. Revell did a decent job in 1/32 as well.