In terms of UK shows - I loved the NEC last year, that was awesome. The summer stuff at Beauleau is always nice too - very relaxing.
I didn't think much of Japfest to be honest, been a few times; as Sir Charles said above, other than the track time (which I don't participate in), the rest is seemingly just a sausagefest of chavs and poorly modified cars with their LEDs flashing and their subwoofers thumping. JAE has never really appealed to me (as a show/venue) - but I haven't been, so can't comment on it. I'm not really into the modified scene (bodykits, lairy paint, LEDs everywhere and flamer kits) which is mainly what it seems to be geared toward and the enticement of 5-a-side football, pub quizzes, karaoke and tug-a-war have done absolutely nothing to gain my interest - you look at the 'activities' on the main JAE website and you'd be led to believe it was some sort of event for under-privileged teenagers, not a car show. I know there's more to it than that and I am sure the camaraderie of our club members make it a lot of fun - as with all club events.
Zedfest I haven't been interested in either for a totally different reason - driving hours to go and camp outside a scout hut.
I'd really like to do LakeZ one year. :)