Not really...I've been using M&F extra light for my starters, and I notice a nice layer of yeast on the bottom, as well as (what I assume are) little clumps of yeast. The fluid above the yeast layer just looks like regular, cloudy beer.
I've got some Cooper's DME on the way, which I plan to keep around for starters. I read in "Designing Great Beers" that Cooper's is the most fermentable extract, so I figure it ought to be good for starters. Note that I found this out after
I ordered it.....I'm not that huge of a geek.