Qi is Qa sometimes, I agree, but I think it's because he plays a character in it and it feels kind of false. Especially the sort of double act between him and Stephen Fry... maybe it's just me... but I still like the show.
I think, though, that he plays Jonathan Creek quite well (of course, whether that means anything to anyone...).
Why not give it a go anyway? If you hate it you've wasted an hour at most.