Latest Eclipse release
I gave the JEE version a go under Ubuntu (eclipse-jee-helios-linux-gtk.tar.gz). The first thing I did was to check for updates and get Subversion and Git support up and running. Installing the Git and SVN clients is getting easier. Just visit "Help" / "Install New Software...", click the "Available Software Sites" link and enable the pre-entered sites for egit and subversive (the search bar at the top will help find them). Once they're enabled selecting "--All Available Sites--" in the "Work with:" drop down will allow the installation of the "Eclipse EGit (Incubation)" and "Subversive SVN Team Provider (Incubation)" packages.
After installation and restart, two new perspectives will be available "Git Repository Exploring" and "SVN Repository Exploring."
Opening the "SVN Repository Exploring" perspective should pop up a window which allows the selection of Subversive connectors (I chose SVNKit 1.3.2). I think this feature may have existed before, but it seems more reliable in Helios. The benefit of SVNKit is that it doesn't require the libsvn-java package to be installed with JNI setup properly. On the other hand, it still doesn't seem to interoperate with the openssh key agent for passwordless access to svn+ssh repositories. Nevertheless, the out-of-the-box experience with respect to loading Eclipse and checking out a project from a subversion repository has improved quite a bit. Hopefully in future releases, Subversive will simply be included by default with the SVNKit enabled by default.
Opening the "Git Repository Exploring" perspective presents a pretty spare screen (similar to the CVS and SVN exploring perspectives). If the goal is to load in an external git source tree, the important action to take first is to right click in the "Git Repositories" view and select "Import Git Repository...". The URI entry box accepts http[s]://, git://, and git+ssh:// style URIs (if not more). Unfortunately, github presents git+ssh URLs without the protocol prefix like so: email@example.com:<username>/<project>.git. It's necessary to prepend git+ssh:// before EGit will understand the URI. I won't go into the details of git itself here, but at this point, it's possible select the branches to be imported. Once imported, an entry for the repository should appear in the "Git Repositories" view, with a "Working directory" subentry. It is necessary to "Import Projects..." from the working directory. This is similar to checking out a location from SVN or CVS as a project. The choice to take depends on the structure of the repository, but once done correctly, the project[s] should appear in the Project Explorer view in the Java EE perspective.
So far, EGit seems to be in a fairly basic state: if you're familiar with git, then it exposes most of the fundamental features necessary to get your work done. I'd eventually like to see it provide a slick user interface to provide a really clean way to interact with remote repositories and the commit stream. For example, I wish EGit would provide, right in the Eclipse interface most of the features of github.com.
Servers view (installing Tomcat)
The "New Server" dialog has been slightly refined in Helios, though it could still use some improvement. When choosing the "Apache Tomcat v6.0" server, Eclipse will now download 6.0.26 to a location of the user's choosing. The download still runs in the background, so errors are reported when the download starts because, e.g., lib/jaspser-el.jar hasn't been extracted because the tomcat zip file hasn't been downloaded yet. Nevertheless, the process seems a bit smoother now. What's more, it's possible to "Download and Install..." tomcat from version 3.2 to 6.0 automatically. I'd like to Eclipse to be able to download JBoss and JOnAS at the click of a button, too. It would also be nice if the Geronimo and Jetty adapters were installed by default, but they're still just a few clicks away using the "Download additional server adapters" link in the New Server dialog.
I suppose that's enough for now, but I'll finish with a bug in the Linux version that should be noted:
In dropdowns that allow text entry (sometimes called "combo boxes"), I've noticed that typing some text that matches an entry in the drop down triggers a popup of the entries that match. In some cases, selecting an entry from the pop up causes Eclipse (or even the JVM itself) to crash. It doesn't happen all the time, but I've noticed it twice in two contexts: 1) selecting the repositories in the "Work with:" drop down when installing new plugins and 2) when selecting previous git repository locations in one of the EGit dialogs. I suspect it's an SWT/GTK issue, but I haven't the time to investigate today.