we've made some drastic changes in the way the "Import Maven projects" workflow in m2e 1.5.0 . Previously, when selecting a directory of projects to import, m2e spent a huge amount of time analyzing potential lifecycle mapping errors and discover potential fixes from remote connectors, before you could even choose which specific projects to import.
That lifecycle mapping analysis has been deferred to *after* projects are imported and it only checks for *actual* errors now, before trying to discover the world. The discovery mechanism itself has also been greatly optimized.
It means the 1st page of the maven import wizard can now refresh in less than a couple second (usually << 1s), instead of up to several minutes.
One caveat is it won't try to discover connectors that for plugins whose lifecycle is already covered. ex: the mavenarchiver plugin won't be proposed for download if the maven-jar-plugin has no errors.
The lifecycle mapping discovery refactoring led to a few internal classes to be deleted or changed in a non backward compatible way, so if you built some m2e extensions over these, you might be badly affected. Check  to see the extent of the changes.
So, please, give the latest dev build a try  and let's know how good or bad the changes are from your perspective.
"Have you tried turning it off and on again" - The IT Crowd