If you're coming from a Windows environment, you're going to be put off by the inability to simply add applets to the top of your workspace with a mere right-click. Instead, this is handled by extensions. Granted, installing extensions in GNOME is brain-dead easy thanks to the simple to use on/off toggle switches located on the GNOME extensions page. Sadly, one must know to actually visit this page to enjoy this functionality.
On the plus side, GNOME shares its desire to provide a straight forward, easy to use control panel. This may not be a big deal to all of you, but it's something I find commendable and worth a mention.
KDE offers users a more traditional desktop experience, with familiar launchers and the ability to get to software in a more familiar way if coming from a Windows desktop. Adding applets (or Widgets if you prefer) to your KDE desktop is a simple matter of right-clicking on the bottom of your desktop. The problem with KDE's approach is, like most things KDE, the feature you're actually looking for is hidden. KDE users will berate me for this, but I stand by this statement.
To add a Widget, I right-click on my panel, only to see panel options and not an immediate method for installing Widgets. I won't actually see Add Widgets until I select Panel Options, then Add Widgets. Not a big deal to me, but it becomes an unnecessary tidbit of confusion for some users.
To make matters even more convoluted, after the user manages to locate the Widgets area they then discover a brand new term – Activities. I have never seen someone new to KDE actually know what the heck this feature is for. Oddly, it's in the same area as Widgets, yet it's somehow in its own area as to what it does.
Now don't misunderstand me, the Activities feature in KDE is actually valued and totally great. But from a usability standpoint, it would be better suited in another menu option so to not confuse newbies. You're welcome to differ, but testing this with newbies for extended periods of time has proven me correct over and over again.
My rant against the placement of Activities aside, the KDE approach to adding new widgets is great. Like with KDE themes, you're able to browse through and install Widgets automatically using the provided GUI. It's a fantastic bit of functionality, and it should be celebrated as such. KDE's control panel isn't as easy as I might like it to be, yet after speaking with a member of the KDE design group, it's been made clear that this is something that they're working on. Yes KDE fans, a need for a simpler flow into the control panel is both confirmed and on its way.
On the flip-side however, I would suggest that if you want a powerful control panel, KDE blows everyone else out of the water cold.
Anytime I talk about the shortcomings of any one desktop environment over another, I receive a flood of email/comments suggesting that I hate the thing I'm calling attention to. Want to hear something interesting? I actually run KDE, GNOME and XFCE on my computers in my home office. I also have older machines with LXDE and OpenBox, too. Each desktop experience offers something useful to me and helps me to use each machine as I see fit.
Now granted, I do have a soft spot in my heart for XFCE as it is a desktop environment I stuck with as my primary for years. But at the time of this article, I'm writing this on my daily use PC and it's default environment is in fact...GNOME.
My point here is that I still feel that XFCE provides a better user experience for someone looking for a traditional, stable and simple to understand desktop environment. That would merely be my humble opinion – your opinion may vary.