Claudiu, well said, that's why in my tinkering I wanted to minimize the amount of hacking required for the plugins and theme files, so I decided to use a theme that would handle the thumbnails work for me, meaning 1 less plugin to have to hack, and then created a custom plugin to handle the feeds, everything from gathering the data to caching it and displaying it on my pages.
There's lots of good themes that will handle the thumbnails, Options is great if you can find it, Mimbo too, and lots of other magazine style themes.
What I did stripped everything down to a single plugin for me. Of course I then added the All-In-One-SEO and Related-Posts plugins too, but neither of those require any hacking or theme mods to use, so I've basically removed all of the hard maintenance stuff from the auto-blog I've been working on.
Of course, the trade-off is that I have to manually create each post title, tag and upload an image for my posts because of how the theme and plugin work, but still that takes almost no time and the end result is a cool looking output that's content rich.
To me, that's the trick to being effective with auto-blogs that you're using for real human traffic, they have to look complicated and like you put a lot of time into every posting to impress your visitors, but on the back end they have to be as simple to deal with as possible to make them worth running for you.