That is explained in the beta changelog.
They say theyre starting at 1.09 but as the bugs are fixed they will work up to 1.1 (Quote Below)
Some Final Notes on the BETA
Impulse will show the Sins update as v1.09. This is normal as we're working up to v1.1. As we put out updated BETA versions, the version number will increase until we hit the final v1.1.
* You will only be able to play multiplayer games with others using the v1.09 BETA (you can still play single-player games too).
* If you run into problems or have other feedback, please post it in the Beta Feedback forum. We will be looking for reports here and if you post them elsewhere, they may be missed.
* You can read over the Change Log here.
UPDATE: If it's taking a long time to download the Sins update, you may want to uninstall the game and reinstall the entire beta fresh. Full installs come off our Cachefly network which has a multiple servers and loads of bandwidth.