It depends on whether I really like the content of the blog or like the blogger...
Generally, I'm not a fan of cluttered blogs. I don't like teeny tiny reading areas for the main body of the blog because there are multiple columns either side of the main body.
I'm not a fan of things popping out at me, constant adsense/advertising crap, tiny writing or harsh contrasts that make it difficult to read the content and leave funny patterns on my eyes after reading the blog for a while.
I like simple, functional, easy to navigate and pretty and I don't give a monkey's ass if a blog or blog article is full of pictures if they are cool, pretty and/or serve a purpose.
However, stylistic preferences aside, it's the content of the blog that matters.
You could have the best blog layout and design in the world but if I don't enjoy what you write, I'm not going to keep reading, it's as simple as that.
If I find your blog layout annoying but you write great reviews, share a similar taste in books, write articles that challenge how I think, write articles that amuse and are a blogger I like?
Then I'm going to keep reading your blog regardless of whether I like the aesthetics or not.
At the end of the day, It doesn't matter if I think a blog is messy, ugly, unwieldy or annoying.
It doesn't matter whether I think a blog's content is crap or not.
It doesn't matter whether I like the blog content but think the blogger seems like a first-class grade-A tit, all that matters is that the blogger is happy doing what they do and that THEY like the layout of their blog.
We spend way too much time on our sites to pander to someone else's preferences if they do not match our own. You have to just be true to who you are and march to the beat of your own drum and if you like harsh contrasts, advertising and clutter then crack on my fellow blogger! Crack on! I'll just do myself a favour and scroll on.