I was very upset to find out that Slype doesn't work on freshly installed OS X 10.9 Maverick Developer Preview 1. However, there's a quick workaround for that issue: Install an older version.
As for Skype 2.8, It works flawlessly. By flawlessly I mean, that the following works:
- Group Messaging
- Group Calls
- File Transfers
I'm beginning to fall in love with that old version of Skype.
You can grab it there: