When you try to install something from Central, it takes quite some time before you're shown the install dialog and can actually proceed.

Mickael in JBIDE-17496:

Maybe you could open an enhancement request for performances. FYI, with Central as it is in JBDS 7.1.1, you still have to wait for those 5 seconds. However, it just changes cursor and freeze UI, you don't see a progress bar.
The performance are most likely to be improved (~divided by 2) when things get actually released and fetched from Akamai.