Hi Adamski! Live and Reason is truly a great combination. They can really work well together, because they are completely different application and they completes well together.
First rule to know is that you always start Live first and Reason second. Live is the master application and Reason is the slave.
There are basically 2 ways to use Live and Reason with Rewire. The first one is to use Reason as a sound generator... not unlike using virtual instruments plugins. You control and sequence all Reason devices in Ableton Live.
The second is to use them in sync. You record your sequence in Reason and it will follow the tempo of Live. Whenever you hit play in an app, it will start the other one and both will play together in sync.
Another great use of Reason that does'nt require using Rewire is to bounce out patterns in Reason and import them in Live for further manipulations using Live's incredible sonic shaping possibilities. Hours of fun!