Is having small, tightly-themed ad groups (10-15 keywords max) the way to go on the content network, as opposed to having 1 as group of 1,500 keywords? Will having nicely organized ad groups improve what pages the ad shows up on, potentially increase CTR, lower CPC, etc? I think the answer is a big YES, but I'm looking for some of you Adwords pro's to chime in with some of your content optimization tips.........
I would say definitely keep a theme in each ad group. If you want to experiment do a tightly-themed group and then a looser one and run a placement report and then visit the sites that are showing your ad and see how related they are to what you're trying to target. A good technique for content is to run some keyword-targeted campaigns and then run a placement report and see which sites are giving you a good CTR and conversions and then do a CPM site-targeted campaign for those sites.