Hi!
This post is about my experience with the KDE 4.4.x, and only lists some very visible (mostly negative) changes. Why only negative? See the end of this post.

Now. The 1st thing I noticed that my manually set login screen was the default debian again. It was a result of replacing an manually edited config file with a new, shipped one. Actually, synaptic asked me if I want to replace the config file with a new one, and I said yes, so nothing surprising happened.

The 2nd thing I immediately noticed is a significantly more sluggish desktop performance. You must know here, that I have some basic compositing enabled, but it should not affect as simple desktop operations as switching between tabs in the system settings tool. But in fact, these (and other really basic functions) were affected. Unlike in KDE 4.3.4, switching between tabs had a visible and really annoying lag (about half a second?). So generally, I noticed a global drop in desktop responsiveness. That's a minus.

The 3rd thing I noticed is an increased memory usage of a freshly booted system (about 20-30 megs). I guess KDE's new, forced-to-use Akonadi subsystem caused it. And here I want to stress the forced-to-use part of the previous sentence. That's a minus.

The 4th thing is the new way of personal info management in KDE 4.4.x. I didn't find a way to shut Akonadi off completely, and roll back to the KDE 4.3.x version of PIM. Why did I wanna do that, one might ask. Well, simply because I don't use anything else related to PIM, than KAddressBook, KMail and Kopete. I don't use calendars, reminders, social desktoping, etc; so the old(er) fashioned way of storing contacts was quite sufficient for me, and was actually very happy with that. For me, running a whole server app to manage my single and simple contact list is very inefficient, and I actually have some security concerns about it (managing every personal info in a very centralized fashion isn't a good idea I think). That's a minus.

The 5th thing I noticed were my completely reset default system fonts. I checked it out with the system settings tool, and all the fonts were reset to Andale Mono. I certainly wouldn't choose a mono font for my desktop. It's a mystery to me why this happened, but definitely happened. Had to reconfigure all of them. That's a minus.

(The 6th thing I noticed was the new applet selector. I actually liked it, and it was more easy to find the needed applet with that. That's a plus. I don't want to mention all of the new features of KDE 4.4.x which are actually helpful (tabbed windows for e.g.), since those are obviously pros and not cons.)

If it wasn't obvious from the start, I never wanted to list all the good additions since 4.3.x, since the changelogs provide that information. I wanted to collect some very observable negative effects of the upgrade, since these are never written in any official texts.

I want to stress out that this post is not a rant, but instead a list of drawbacks of such an upgrade, and I'd like every reader to add their own experience in the replies, or simply add their opinion of my observations.

This list is far from complete and I never told that I noticed only these contras/pros, I only summed up the most visible ones/most important ones (to me). Keep this in mind. Thanks.

You may want to turn off the search function. My desktop is much faster that way and I have a very underpowered laptop.

Yeah, I turned that off, but still, it was very sluggish. I admit that neither my laptop is a very powerful one, but if KDE 4.3.4 works relatively fine, than why KDE 4.4.x isn't? Perhaps the KDE developers should consider treating system performance as importantly as adding new features...