Cogito, ergo sum
UDE is a largely un-used IDE for one simple reason. It is no good! Well, at least the UT2003 version. The reason, I assume is that the software was underdeveloped for its boundaries, and crashes all the time no matter the situation.
Good news for UDE
Those of you who don't know, Dean "Harmeister" Harmon, creator of WOTgreal, was commissioned by Epic to write the UDE for UT2004. This is fantastic news, as WOTgreal is one of the best and most stable UScript editors available to us. Below is a clipping from his web page.
Friday - Jan 30, 2004
The News is Out... 8:38AM
Well, I was kinda hoping this would wait a little longer (like when the game ships), but it was Epic's cat to let out of the bag, so... As stated in the chat with Epic and NVidia last night (better formatted log from UnrealOps here) UT2004's version of the UDE will be none other than a branded version of WOTgreal. (great, now *I* get blamed for the bugs instead of DrSin :) ). It will be pretty much the same as the current development version, just re-branded as the UDE.
So to clarify, though, WOTgreal still exists and will continue to exist, Epic is just licensing a specific version of it. They won't get any new versions with new features and whatnot, just bug fixes (let's hope there aren't too many bugs that need fixing *crosses fingers*).
So I want to thank all those who have sent feature request and bug reports over time, you've definately made a difference!
The UDE has been released. Download it here: 
You will also need the UT2004 UnrealScript Source in order to use from of the advanced programming features (like code-insight and completion).
Draeath: UDE doesn't seem to like the UT2004 packaged with the Unreal Anthology (or the default WOTgreal profiles either) - it appears to be because they didn't put the origional individual uninstaller entries in Add/Remove - they only put one "Unreal Anthology" master uninstaller which incidently removes the whole shebang. To fix this, copy and adjust the uninstall registry information from the origionals, and adjust paths as needed. As an added bonus, you can then remove individual parts of the anthology now.
Bob_The_Beheader:Hmmm....Compared to WOTgreal, how exactly is UDE2004 different? They look identical. If they are indeed the same, I would pick UDE over WOTgreal simply because I don't want to pay the registration fee. :)
Sweavo: Judging by the text above, WOTgreal will get new features, UDE won't.
vitaloverdose but with wotgreal dont you have to register or it takes a long time to open each time you run it?
El Muerte: yes, WoTgreal doesn't require registration (more or less), as for the rest, UDE is identical to an old version of WoTgreal 3.005 (newer than 3.004 but much older than the current 3.005).
T1: UDE seems to broken if you aren't using it for UT2004
El Muerte: yes, that was somewhat the deal
rejecht: I had trouble installing the mod (UDE3005.UT4MOD) for UT2004. Short story: The installer got the version from manifest.ini, where version = 1, however, the installation had all patches installed (v3369). I could set version = 3369 in my case, and the installation would proceed, then ending up creating a subfolder called UDE under the System folder.