I did a quick comparison of the indexing speed between IDEA 9.0.3 and IDEA X EAP 96.802 by "Invalidte Caches" and restarting IDEA.
Then I started timing as soon as it said "scanning files" and then stopped when the "updating project indices" background task finished.
My project is pretty large with over million lines of code and 10,000+ java/actionscript/mxml classes. Also, the JDK and Flex SDK libraries
plus over 100 third party java and flex libraries.
IDEA 9.0.3 took 9 min 50 sec to reindex .
IDEA 10.X took 5 min 0 sec to reindex
So, based on quick test with a single datapoint (YMMV), IDEA 10.X is indexing 100% faster than IDEA 9.0.3 !!
Good job, Jetbrains!