?
Sure, here are the main ones as of v4.0.6 which we released ealier today:
OData output caching may be optionally configured in Advanced Settings that should improve package installation performance since the NuGet client (both .exe and VS extension as of v3.3.0) always issues 2 identical requests when querying for package data or downloading packages
ProGet now respects the NuGet client's Accept-Encoding header which has recently added gzip; this may reduce package download times considerably
Currently, the biggest bottlenecks on performance are related to connectors reaching out to NuGet.org, especially when combined with connector filters. Connector filters especially may cause slowdowns if the connected NuGet feed does not optimize the OData "startsWith" filter.
In a future version, we are planning to have scheduled tasks index NuGet.org so that connectors can be filtered in ProGet's database, which will be instant in comparison to a basic 3-filter connector query.