Everyday is different at the character warehouse. We've been 6-7 times or so. Some days have been awesome and we scored some cool merch at great prices. Other days, I've searched hard to find anything worthwhile.
It's always busy and yes, being there at opening is key. There are actually two outlets. One is off Vineland and closer to WDW and the other is off I-4 and closer to Universal. We like the one by Universal better. It's not quite as busy and it's actually a bit smaller but we've found more that we liked there.