Have any of you tried raw therapee? It works really well and is cross platform. The only thing I don't like about it is the folders are not sorted in linux, but the author said they will fix this soon.
You can get photoshop cs2 running with wine now pretty easy. Not sure about lightroom, but setting up vmware or dualboot is cake. I use cs2 under vmware and it is very quick.
I use kubuntu myself as I think KDE is a better gui than gnome, but both are very good. Switched away from windows about 11 months ago and it has been great. Updates can sometimes cause problems, but viruses and spyware is now non existant. There really hasn't been anything I have missed except for the adobe stuff which I vmware or dualboot for. Here is my list of must have apps:
MythTV: What else can I say, MythTV is the best PVR software out there and it just plain rocks. All the plugins and extras are amazing. I installed the web front end component for it and now I can watch/listen to all my videos and music through a web browser from anywhere. It auto transcodes and streams it on the fly. I can also schedule program recordings and stuff. Another amazing plugin is called zoneminder. It lets you use the mythweb frontend to let you monitor your home remotely with security cameras and watch a live security feed through a web browser:
http://www.zoneminder.com/screenshots.html
FreeNX: Basically it is remote desktop for linux. It is superfast and rides over ssh so very secure. I use this all the time to do stuff on my server.
Blender: 3D modeling and animation software. This thing is unbelievably advanced...check out the screenshots:
http://www.blender.org/features-gallery/features/
Vmware: Couldn't live without it.
Raw Therapee: The interface is allot like ACR with many of the same features.
Digikam: I don't care much for the photo editing tools except for quick stuff, but I love it as a photo manager and prefer it to bridge and lightroom.
Inkscape: If you don't have the newest Adobe Illustrator and need to do vector graphics
this is the best.
OpenOffice: Where as many MS office programs make me want to kill myself, OpenOffice is a pleasure to use. Unlike Word which is unfuriating , you can actually type in Writer without it jumping 10 spaces and inserting a bullet. And when you hit backspace it will actually consistantly delete the preceeding character, imagine that! Calc is allot better than Excel for me as well. Things in the menu tree are easy for me to locate and it is much faster. I needed to do a find replace for a database project on 200,000 records. In excel this took my computer close to 5 minutes, in calc it took about 35 seconds.
Konqueror: This is what explorer in windows should be.
Apache/PHP/MySql: If you do web programming, this is where it is at.
Samba: This way if any windows or macs get to your network, they can all share
each others files.
Kaffeine: My prefered video player.
Amarok: The best music player I have seen. It is kinda like itunes but better. More feature rich, better interface, and you can use any media player, not just an ipod. Works great with my archos and clix.
Google Earth: Love it.
Amule/Ktorrent: For all your p2p needs.
If you go for ubuntu you might want to check out Automatix2. It sets up allot of codecs and other odds and ends for you in a few easy clicks. If you are a noob this is a very nice thing to get up and running.