There are tweet ads, yes. They are usually marked as "promoted"
I found it useful to "report as spam" the account they were coming from so at least you only see them once...
I found the new layout to be headache inducing for my english-speaking, left-to right-reading brain so I switched to the Chrome plug-in Silverbird on TVGugs recommendation... and haven't seen the promoted tweets since. Maybe that's because I'm using lists more... but it solved a lot of problems for me.
For you Mac folks, there's a new dicount bundle from MacUpdate: 11 Mac Apps for $49.99 (mupromo.com) There's some good stuff here, actually: A Better Finder Rename 8.78 Civilization IV MacUpdate Desktop 5.0.8 DVDRemaster Pro 7.0.