I suppose the thing to do on MU is to leave a review for one update and change the review if things improve. I feel slightly uncomfortable leaving an app review that I can't revise.
As you can see from my comment below, I was looking forward to getting the license issue sorted out so I could use WhatSize. I really liked this app. Even though other apps I use, such as Path Finder can organize folders according to size and perform measurements like WhatSize, WhatSize generally made (and still makes) navigation much clearer. It's much easier to find that rogue ballooning folder!
You'll notice I used the past tense in the last paragraph. I'm a little baffled by the changes in V6. I can still see files well, and navigation is still intuitive, but some basic things are gone. The delete icon in the toolbar, for example, or the entire view menu. You can change some icons, BTW, but there is no delete to be found! In fact, the lack of helpful icons gets to be a little annoying. There are magnifying glasses next to the main folders in the sidebar, but no helpful show in Finder icons anywhere else.
I'm also finding a few little bugs that could be Yosemite related. I can't add folders to Favorites from WhatSize, I have to drag folders there from the Finder. I can't measure one folder in the favorites sidebar anymore either. If I try to measure one, WhatSize starts measuring my entire HD.
I can't say I noticed a cleaner function in the previous version. This version has one, but I'm stumped as to how I supposed to customize it. I used the cache cleaner today and discovered that it has two settings, partial nuke and nuke. Partial means it just clears out everything from the user cache. Nuke wipes out everything. Too bad if you want to spare a few things it picks up in the search! The other cleaner functions appear to be the same. The other strange thing about the cleaner function is that the helpful colorcoding from the browser is gone.
Although the interface for basic functions is a bit puzzling, the actual sizing function is excellent. I wish I could tell you why WhatSize makes my filesystem more legible to me than Finder or Path Finder or Fork Lift -- maybe its the pleasant colour coding? -- but it does.