Don't really use them, they have a novelty value, but the truth is that it's mostly anyone's guess how they would really have performed (probably badly), so it's a bit too far in the realms of fantasy for my liking to use them, given that their performance in the sim is largely a wild guess.
Even 'exotic' Nazi aircraft such as the Heinkel Salamander, which actually made it to limited use, were at best shaky, the one the RAF tested post-war crashed killing the test pilot when it fell to bits as he rolled it. The fans on the Me 262's engines were known for disintegrating, often with fairly disastrous consequences, and the Me 163 Komet was probably more useful to the Allies given the amount of pilots it killed, often in a very grisly fashion.
I'd be interested to see how some of those designs perform in X-Plane, given that X-Plane does actually calculate flight characteristics based on the form of the aircraft.
Chock