all depends on how good your DSL server provider is. It varies from different parts of the world.
For the most part though, it will be a HUGE improvement for you from a 56k modem (that means 56kbps) which is 7KB max.
If you're lucky, you can get one of the 1.5Mbit connections which is like 180KB or so max. Myself am using a cable connection at home at 512kbps (64KB max) but only averaging about 200kbps lol (have one of worlds worst ISPs lol).
Nonetheless, it's still faster than a dial-up modem.