My bro and I went to Florida over the break.  Islands of Adventure was good, but we agreed that the Hulk is overrated.  I don't know why, maybe just because it's launched and doesn't provide the "warm-up" of a lift hill, but we didn't find it too exciting.  The Dueling Dragons on the other hand...best inverted(s) out there!!!  We also spent a day at Sea World and found out that the Kraken is the best non-Millennium force sit-down out there. 
 
Busch Gardens was also good.  Gwazi and Kumba were both worth the 20+ rides we got in on each.  But Montu was closed for maintenance!  Needless to say, we were quite PO'ed. 
 
After being at those parks I might never go to one during peak season again.  Every ride was a walk-on, Sea World and Busch Gardens let us re-board the coaster if any seats were open (which there almost always was). 
 
But I've never been to a seasonal park out-of-season.  Does such a time exist for seasonal parks?  If so, when's the best time to hit them?