I use a mix of odd sized banners, pure text links and css styled text links with padding and hover colors...to make it 'graphical'.
I almost always attach a text link to the <a> tag on banners.
I'd never use a standard sized banner as the sole advertising source on a page.
I think larger banners like a hpa or fpa resized to 400x240 or thereabouts can be an effective tool especially if it has some good ad copy.
When my HD died I used an old pc running in 800x600 and happened to look at a couple of my free sites in that resolution and was hjappy with what I saw.
Maybe one reason text links get more clicks is because the surfer doesn't have the visual cue from the banner so even if it's a sponsor he's seen dozens of time before he'll have to click the link to see the sponsor.
If the sponsor has a good entrance page and tour perhaps that'll snag 'em.
All that stated, I tend to put heavy emphasis on the ad copy text links and view good banners as a compliment to my ad copy.
I bet a pure text link free site is a little refreshing to the surfer. Many banners are just an obnoxious
SALES tool people beat them over the head with.
Pure text sites must seem 'ad free' to joe surfer. If the ad copy is good then the text will help work them up and seems part of the content as opposed an annoying ad tactic.