Thanks in large part to the talented Nick_vh who is interning with Acquia as the final stage of his master's degree, we've been making progress on a number of outstanding issues for apachesolr 7.x. If you are using the module, please take a look at http://drupal.org/node/1293570 which lists remaining issues to be included in the next beta release (possibly the end of this week).
The patch to improve custom search pages includes a number of re-arrangements for the UI, so please try it out: http://drupal.org/node/1294846
A few other significant features are in the work for RC1 (when the intent is to freeze the API and schema). In particular we want help with Separate indexer for multiple entity types
Once apachesolr 7.x-1.x is at RC1, we plan to work on a 6.x-3.x back-port that will enable multisite searching across Drupal 6 and 7 sites.