The feature/command I use the most is "pget".
The option "n" accepts an integer which defines the number of parallel connections to be created.
Some servers limit the bandwidth allowed per single connection. Creating multiple connections for a download allows you to multiply the download speed too.
This is the syntax:
lftp -e 'pget -n 3 http://goo.gl/PVk8Q'
This is only an image so you won't see much difference but try with a bigger file...