Is there a slight difference in meaning between "1" and "2"?
1. It is as if you are lying to me
2. It seems as if you are lying to me.
The only case for using 'seems' seems to me to be if you're stressing the possibility of misinterpretation - 'It seems as if you are lying to me, but I know you wouldn't do that' - or if the interpreter needs to be identified ('It seems to me/you/him/her etc...')