As a CleanMyMac user, I thought I would take a look at this as both sport very similar features, and as someone who regularly tries out and uninstalls a lot of software, I was particularly interested in the 'leftovers' feature, and was interested to see if Dazzle would find stuff that CleanMyMac had missed.
Unfortunately the resulting list of files that Dazzle proposed to delete as traces of 'no longer installed' apps gave me some cause for concern, not least because most of the files it wanted to remove belonged to apps that were still installed! It offered to remove parts of Photoshop Elements, iStatMenus, CleanMyMac (files belonging to the Disk Watcher and Trash Watcher processes), Hazel and various others and had I just hit the Erase button following Dazzle's recommendations, I'd have probably made a few problems for myself. Hazel in particular seemed to be an issue because Dazzle wanted me to delete all of Hazel's support folders (e.g. Logs, Application Support etc.). On top of this it suggested deleting some PDF files I'd created (no idea why) and it even wanted to delete parts of itself, like com.kallaxa.DazzleHelper.CleanupReminder.plist and MonitorTrash.plist. To be fair, it did spot one app I'd recently uninstalled that had left behind one file, although this file was also spotted by CleanMyMac when I compared its results. In fact CleanMyMac spotted files belonging to 3 other apps that had been removed recently that Dazzle had missed.
Another issue was that I was using iTunes and had PathFinder open in the background. Out of the blue, Dazzle pops up a dialogue saying "Uninstalling Path Finder by dragging it to the trash will leave behind preferences, caches, logs and other items behind! Would you like to correctly uninstall this app and related files using". Firstly, I hadn't dragged PathFinder to the trash, secondly I wasn't aware that Dazzle (which wasn't running at the time) had installed a background agent by default.
Given the somewhat over-zealous results above, I've been rather loathed to use any of Dazzle's other features in anger. That said, I have a quick look at most of it's other features all of which appear reasonably standard in terms of clearing up cache files, log files, extensions, etc., and for the most part its results looked similar to those of CleanMyMac although I didn't drill down into the detail.
In the end, even though Dazzle is around $10 cheaper (when it's not on offer) that CleanMyMac, I wouldn't switch to Dazzle. I get the impression that as a version 1.0, Dazzle still has a few rough edges that could land an unsuspecting user in trouble. Perhaps subsequent versions will address this?