2010 Lakers: 41-13 pre ASB, 16-12 post
2009 Lakers: 42-10 pre ASB, 23-7 post
2008 Celtics: 41-9 pre ASB, 25-7 post
2007 Spurs: 35-18 pre ASB, 23-6 post
2006 Heat: 32-20 pre ASB, 20-10 post
2005 Spurs: 41-12 pre ASB, 18-11 post
2004 Pistons: 33-21 pre ASB, 21-7 post
2003 Spurs: 33-16 pre ASB, 27-6 post
2002 Lakers: 33-13 pre ASB, 25-11 post
2001 Lakers: 31-16 pre ASB, 25-10 post
2000 Lakers: 37-11 pre ASB, 30-5 post
Don't know what your threshold is for "great," but I'd say it's winning 75% of your games... and the 09 Lakers, 08 Celtics, 07 Spurs, 04 Pistons, 03 Spurs, and 00 Lakers all had great records after the break.
As for "peaking," the 07 Spurs, 06 Heat, 04 Pistons, 03 Spurs, 01 Lakers, and 00 Lakers were all a lot better after the break than before.