So, er, does the scroll-lag in the Steam client induce seizures in you, or is this just an aesthetic quibble?
You could alternatively use http://store.steampowered.com/
— seems quicker on my end, that.
/edit: I linked your vid over at the Steam forums
where there is an ongoing thread about the issue (a dev posted in the thread, so he might see the updates). I, too, am seeing pretty high CPU utilization in the client on several different computers, and while I'm not too bothered, having a more efficient client would be nice.