I use Jerboa the most, Liftoff and Connect see similar usage... though liftoff gets a bit more. It's not a case of Liftoff being the only actively used app though, or even the most actively used app.

I use them all enough to have maxed out a few hundred megs of cache. But it seems quite likely to me that other apps are doing a better expiring data from their caches than Liftoff.