I'm currently developing a site where each users signed up gets their own personal profile page, each page has a google link unit at the very top as a default for the template. I'm still checking other ads where it won't be as obtrusive as possible, but do you think google link units are profitable?
They definitely are profitable because they tend to fit at good places and it all depends on how well you can incorporate them. My vote would be to use as per your design and put them well into the site.
Im not sure why but i always liked adsense ad units more then link units, maybe because its bigger or something, but remember, bigger aint always better
link units also performs bad in my site...but it all depends in the placement...and visitors who clicked on link units are the true target visitors...