Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
I can't speak for Ubuntu Gutsy at all. I like KDE, use KDE, and have even written (a very small amount) of KDE/Qt code.
In the past, I've never got very far with Kubuntu because it just didn't have the flexibility that I so prize in a KDE desktop. It was crippled, and locked down in many ways. And, I didn't want to take the time to figure it all out, and make it work the way I like. But, the Gutsy version is better. I can actually go to /usr/share/applications and drag a KDE .desktop applicaton file icon onto my desktop and have it be visible (without having to open it in kwrite and change the NoDisplay property from true to false). The only desktop application icon file I've found set to NoDisplay=True is the konquerorsu.desktop icon, which is konqueror in filemanager mode running with root priviliges. I set it manually, and I can live with that.
I have a Gateway FPD2275W 22" wide monitor which I run at its native 1680x1050 resolution. The Kubuntu Gusty install picked up on this, and allowed me to select to install the NVIDIA proprietary driver--this was seamless and flawless.
What do I miss? Well, I'm getting kind of old and set in my ways, but I have always liked the (now old) KDE KWin style called thinkeramik. But this doesn't seem to exist for Kubuntu (nor for Debian in an x86_64 version). Again, I like my eye candy, but I can live without thinkeramik.
Multimedia is much easier to set-up and configure in PCLinuxOS. But, one of (K)ubuntu's strengths is its popularity--this means there's lots of help out there on the 'net. You can usually do a Google search and find information that will help you quickly. And, that's what I did. Some command line work here, but, right now, I'm watching Wallace & Gromit's "Curse of the Were-Rabbit" ("I need more cheeeeese, Gromit!") on Kubuntu Gutsy using Kaffeine and then KMPlayer.
I also installed flashplayer. Since I'm using the 64-bit version of Kubuntu gutsy, the nspluginwrapper (for 32-bit compatibility) was installed as a dependency. It works fine, though I had to tell Konqueror to scan for new plugins.
I had an old Windows XP partition on the drive. Kubuntu Gutsy picked-up on this. Access to the Windows partition from Kubuntu works well.
My favorite recreational game (maniadrive) is missing from Kubuntu. I suspect I can go to maniadrive's web site and get an installable version.
So, am I ready to abandon PCLinuxOS and make a jump to Kubuntu? No way. For me, PCLinuxOS is just better.
Though I'm not a Linux newbie, PCLinuxOS is without peer as a distro for newbies. And it's very powerful and reliable for experienced users who just want to get work done and who don't want to spend a lot of time tinkering to get things working.
But, to be fair, PCLinuxOS has its limits--it's not currently enabled for non-English speakers, there's currently no 64-bit version, and while it can be used as a server, it is primarily a desktop distro.