I personally not run one but I've ridden in an LBZ that had one and it seemed like it was a bit quicker to spool, being a billet wheel it's naturally going to spool up faster than a stock one, but the blade design is different and geared to move more air with less back pressure...so I don't know if the spool time was actually quicker, or if it just made more power sooner and the truck felt quicker overall...
So I'm not so sure your spool time "significantly" increases with a Batmowheel, as much as the max boost pressure and overall volume of air moved does.
You'll definitely notice power gains through the mid and top end.