If you’ve never used Skype before, it’s a virtual phone service over the Internet. It also includes instant messaging, with avatars, as well as having a huge range of plugins, from games, to MSN Messenger and even a remote control application (called RemoteX) which can be used in a similar manner to Remote Desktop or VNC.
The first main difference that strikes you between 3.8 and 4 is the main window. On version 3.8, the main Skype window was essentially forgettable if you were using it as an instant messenger program - you could open your messaging session separately, chat way, and completely ignore the main window. In version 4, by default, they’re docked into the main window, which now has a more MDI feel about it than the previous version. it takes some getting used to , but whether its easier or harder to use depends, I suppose, on what you usually use Skype for. It’s obvious, though, that they’re thinking more about video calling and trying to ensure that you don’t miss calls or chats, something that I’ve done a couple of times in the previous version. (You can actually undock conversations, which is quite nice, and presents you with almost the same conversation window as Skype 3.8).

The new right-hand pane (which I’ve shown above with the directory pane) is used for conversations, for the directory, or for just about almost anything that was previously a separate window in Skype. While it’s a tidier, nicer interface - and feels a bit less Windows 3.1 - there’s still a few things, especially extras, that open their own windows outside Skype. The good news is that they haven’t changed the extras API, so there’s no need to immediately update every extra you’ve got installed - I haven’t had any problems with them.
Still, this is beta software - and as usual with beta software, things need fixing. What’s wrong with it? Well, not much actually. They’ve started adding help text to the right-hand pane when there’s nothing else open, and that’s quite nice, but it could do with a bit more work; it’d be nice to have links through to context sensitive help. The welcome screen does a pretty fair job of explaining the new features in Skype, but as with the new right-hand pane, the text sizing needs work as on my screen it tends to overlap other text or the control buttons if you’re not full screen.
There are plenty of new features in Skype 4, but there are some missing from the beta that are in 3.8, such as the IRC chat style, contact groups, Skype Prime, and so on (see this list for more details). If you need an accessible version of Skype, stay away from this beta - presumably this is something they’re working on but haven’t got ready yet; the same’s true with the “send money” function, or the ability to view Outlook contacts in Skype, neither of which has the same level of mass appeal as accessibililty functions, but will undoubtedly be deal-breakers for some.
Would I recommend upgrading? Well, I can’t see any reason not to. The new interface takes some getting used to - my first reaction was that they had decided to try and see how hard to use they could make the new version compared to the previous - but once you get used to the fact that everything is in the same window, that the instant messaging view shows contacts at the top, instead of on the right, and lots of other little changes - it all feels fine. As well as trying it out on my laptop, I’ve already rolled it out to my production machine and am using it during work time (I actually don’t use Skype for personal reasons, only for work, as it happens).
My verdict? It’s coming along, nicely. Feels a bit slower than 3.8, but it’s likely that debug functions are turned up to 11, which is only to be expected from beta software. Beware of the functions that aren’t implemented yet, and don’t upgrade yet if any of them is a deal breaker - I’m sure most of them will be back in the finished version. But it’s worth a look, and if you do upgrade you can give them feedback and help influence how the final product looks.