I freshly installed NetBeans and opened my Maven project. No need for some sort of special import here. I simply choosed File | Open Project and selected the project folder containing the Maven root project. NetBeans even marks all Maven projects in the tree with a special icon.
The import finished amazingly fast. NetBeans analyzed the project structure for while after the import in a background process, but nevertheless I could immediately start to work with my modules.
In my case Maven could not find some dependencies in my local repo, which is OK (I did some cleaning up the days before and obviously I was little bit to rigorous). Additionally I was only kind-of online during the tests.
Next, I took a look at the folder structure inside one of the modules. Obviously, NetBeans knows a lot more about Maven projects than Eclipse/M2Eclipse. For example, it knows about generated-sources right out-of-the-box. Even more important, it knows that Maven maintains separate dependencies (and classpaths) for "normal" modules and for tests.
The latter one is in my eyes really important. The Eclipse builders don't distinguish between classpaths for modules and for module tests - regardless if you use Maven/M2Eclipse or not. In consequence, you will regularly run into issues where the Eclipse builder runs flawless, but the Maven build will not. This is just because some of your modules coded in Eclipse reference a dependency with test scope. Eclipse will not recognize this, but Maven will. And NetBeans, too. I like that!
Besides the more or less cosmetic features I was especially interested in how NetBeans performs compared to Eclipse/M2Eclipse. To test this I did some simple refactorings in a central module of one my biggest Maven projects. Since this module is referenced by nearly all other modules, the builder gets a lot of work. In Eclipse this means, that for all dependent modules the M2Eclipse and the internal builder is invoked. This works OK, but again, it is anything from smooth. My first tests in NetBeans have been quite encouraging. First, the refactoring worked nearly as fast as in Eclipse. Second, the build really executed in the background. That is, I was able to continue working during the build. Next, the build completed in seconds, not minutes.
After these basic tests I played with some of the other features. One thing I would like to mention is the dependency graph in NetBeans. It works similar to the one from M2Eclipse, but adds some useful features. For example, it zooms out an artifact and all direct dependents from the graph if you select it (and dims all others). It's hard to explain, but very cool and useful. Try it out yourself!
I also found some features of M2Eclipse that are not supported in NetBeans (at least I didn't find them). There is no such thing as a full-blown POM editor. NetBeans has a POM editor, but it "just" supports editing directly in the XML. The XML editor has a lot of features, like inserting new dependencies using an artifact search. This is perfect for me, since I never used the comprehensive M2Eclipse editors, but I know many people do.
Summary: I am quite impressed about how well-integrated NetBeans 7M2 and Maven 3 are. Both the functionality and especially the performance are in my opinion better than what you currently get with Eclipse and M2Eclipse. But please keep in mind that this only reflects my experiences of a first try. Certainly, if I start working with NetBeans more intense, more problems will arise. And, of course, a new release of M2Eclipse will be out soon, maybe this fixes many of the current issues. But still: I think NetBeans 7 is well worth a try for all developers that rely on Maven as a build system.