There are two feeds that I read regularly which have just been through a site redesign. Jeremiah's web strategy blog and Lifehacker.
Both of these have gone about it in different ways.
Lifehacker went big bang and just changed the site overnight, loads of comments mostly negative.
Jeremiah set up a beta version and got his readers to comment on what they think of his new design before it goes live, quite a few comments mostly positive.
I read all my feeds in my aggregator, bloglines is my personal preference, so I never see the sites and therefore never see the design. I guess that people's reading patterns are similar in that if they search and come across a site then the design matters but if they’re regular readers then they will read the site in an aggregator and not see the design.
Are the comments made by people who just come across the sites or by regular readers? To me having skim read the comments it seems as they are people who are regular readers.
You could argue that without a great design then those people who come across your site by accident will never come back.
The design doesn’t matter and that it’s the content which will make people come back.
It was the surprise where Lifehacker for me went wrong. To their regular readers it all came as a bit of a shock which caught them off guard and this shows in their reaction. It would have been better to have got their views and buy in first as they would have then gone out and promoted this new design as they would have felt it was their decision.