You should update the program to avoid version mismatch. This is especially important with regards to authorization because the authorization system starting 6.9 has significantly changed as compared with 6.8 and earlier and some more advanced auth options may not work as expected.
The current version is 184.108.40.206 so I recommend that you download it and update Viewer and Host.
Believe me, when we have the Mac beta ready for public release we won't delay it one day :) Mac version is indeed what we are currently working on now, this is the highest and current priority now that we have finished with 6.9/6.10 release with its significant revamp of the authorization system (it was a necessary improvement, no less important than Mac support).
This is because the resolution on the remote computer screen is lower than the resolution on the Viewer screen, and you are viewing the remote desktop "pixel-for-pixel". You should enable the stretch mode to fill the entire desktop on the Viewer side.
Right click on the connection item in the address book, select Properties -> Modes -> Stretch.
Note, however, that this way you are simply stretching the image, not adding more pixels (graphical information) to it. So the image may not look as crisp as you would expect if the remote resolution were the same as the local one.