Yes, relevant backlinks to the niche really helps to increase your PR as well as SERP too rather than using OFF TOPIC backlinks... but, it is hard to get niche related links... However, big G will help you a lot to get it....

Mix backlinks...

Don't just rely on relevancy, back links should be mix.

You should have more relevant back links, but you should also get non relevant back links, that's why Angela back links works so well!

Think natural and emulate that.

Agree with stephen.
If you ever read / watch 'stompernet' SEO strategy is being 'natural'. Means that you mix between related site and non-related. And also remember to 'grow overtime' your backlink as well.

Without backlinks you are getting nowhere! Most profitable niches are crowded and most of them just differ in backlinks.

Brightlife

Ive never found that you need relative backlinks especially seeing as most of the backlinks i get are from profiles over blog comments etc.

However i do get some relevent traffic portal backlinks as i call them from blog's just to feed some traffic in but still my sites always rank highly.

Tom Brite

I've been using Paul and Angelas back links which are not related at all and am getting top positions for my keywords for sites in google.co.uk

They work you just need to get it done.

Gavin