When you inport large amounts of hand histories, database index goes broke every 200k-300k of imported hands. These leads to such errors as
"E:\poker\hh\z04.txt ERROR: XX002: index "playerhandsflop_pkey" is not a btree"
"E:\poker\!!!hands\titan_sh\z\iPoker_NL100_SH_to_NL 400_SH_2008-06-01_to_2008-06-30_36k\Titan_SH_NL100_050708\_TURBO__Santa_Claus_0 5_07_2008.xml ERROR: XX002: index "handhistories_pkey" is not a btree"
Of course you can make a reindex of db, and continue the importing, but when I imported 5M hands, had to make the reindex of db 12 times. That's really annoying.
Also the importing of pokerstars hh is 3 times slower than importing from other sites.