The addon has been rewritten and will be renamed to Plumber.
This is a beta release, please report any bugs you may find.

Improvements

Major performance increases: typical VMF map import time reduced from 5-30 minutes to 2-30 seconds.
Manual game configuration no longer required: the addon automatically detects installed Source games on Steam.
No longer depends on other addons to import models: a built-in MDL importer has been implemented.
No longer caches anything on disk.
MacOS support in addition to Windows and Linux.

New features

MDL importer with animation support.
Game file browser: easily import MDL/VMT files straight from game files without manual extraction.
Option to remove animations or animations and armatures from dynamic props to prevent problems when exporting maps outside Blender.
Option to merge solids into one mesh object per brush (enabled by default for better performance).

Enhanced QC importer: removed due to the new MDL importer.
Enhanced AGR importer: missing, best way to reimplement this is still under consideration.
Reusing previously imported data: missing, will probably be added back later.

Imported texture file format is now TGA instead of PNG for better performance.
Switched to custom VDF (Valve KeyValues) parser, which fixes the current parsing issues.
Game files are no longer indexed, and are instead searched for on-demand, leading to better performance.
Importer is now multithreaded.
Importer backend and Blender glue code are now separated, possibly allowing reusing the backend for other projects.
Mostly written in Rust for better performance.