I do a lot with Apache Maven, and I kept hearing about how Nexus helps with better managing your local Maven repository, especially if you go offline a lot, which I do. I was pleasantly surprised as how easy it was to setup and that it did actually seems to speed up my Maven project builds. Sad to get excited about a product that actually does what it claims...
My needs are pretty modest in regards to Maven, and most of the Maven projects I deal with are small, so normally dealing with annoyances of offline and/or configuring m2eclipse to know about the 2 other Maven repos I use isn't that bad. However, when I started trying to build all of ServiceMix (24+ Maven projects) and started to see lots and lots of waiting on downloading various dependencies, I decided maybe I'd see if Nexus could help.
The install of the Nexus Open Source is very straightforward - untaring a tar ball - and starting the Nexus server was as easy as bin/nexus start. Sonatype provides a great (free) on-line book on Nexus - Repository Management with Nexus - that provides good instructions on installation and initial configuration. There isn't much configuration by default except for modifying your Apache Maven ~/.m2/settings.xml file to use the Nexus server versus looking on the Internet for dependencies.
The biggest challenge I had was since I was dealing with a large project which references ~12 other Maven Repositories (Nexus ships with Maven Central and Apache Repos configured) I had to add in those other repositories into Nexus so it could proxy them. Again the Nexus book provides a great section on how to know your missing a repo entry and how to add custom repos into Nexus. After I did a couple, it was very straightforward to figure out the other 10 or so custom repos that ServiceMix requires.
What I saw was that now with Nexus it felt that the ServiceMix built went much faster - maybe 10-20 % - I guessing mostly from just quick all local machine lookups on dependencies. It also felt that Nexus was a little smarter about how it downloaded dependencies from the Internet, not positive on that. Regardless, I noticed a build speed up and a dramatic reduction in network traffic during the build.
I also saw that using m2eclipse was much easier, which makes sense since both Nexus and m2eclipse are developed by the folks at Sonatype. m2eclipse will use you personal Maven ~/.m2/settings.xml file, which in my case is now configured to use Nexus, so I automagically get access to all those custom repositories I already configured in Nexus without having to painfully add into Eclipse. This is nice as I can now lookup archetypes in non-Central based repos, and do the "so what dependency do I need to add for this Class" search as well on non Maven Central hosted dependencies.
Overall a positive experience. Nice work Sonatype!