Snow Leopard looks like a pretty minor change to Leopard on the surface, but "under the covers" there are significant changes. The good news is that applications like MacDive and Mac DiveLog seem to be working just fine under Snow Leopard. I have been able to download my dive computers and sync with Dive Log on iPhone via Dive Log Manager without any problems on Snow Leopard. The one place where changes to the lowest levels of the OS can be a factor is with device driver support. I've been using Suunto's USB cable to sync my D9 with my Mac and the diver that I've been using works fine under Snow Leopard. I have been in contact with some users that have been using the CustomIdea cable and driver that have not been as lucky. The CustomIdea cable uses a chip and driver from Silicon Laboratories. A recent communication with Silicon Laboratories suggested that they were planning to support Snow Leopard and expected to have an schedule for that support around now. I'll let you know when I hear more details on their plans.
VMWare Fusion running Windows and Diving Log on Snow Leopard is also working very well. I've had no troubles importing dives from my dive computers (Suunto and Scubapro/Uwatec) and syncing the data to Dive Log on iPhone.
VMWare Fusion 3.0, Windows 7 (x64) and Diving Log 5.0 beta ... works great too! This was a pleasant surprise as everything worked without any drama. I must confess that I was a Windows Vista "skipper", so I had to approach the upgrade to Windows 7 as a clean install. This was probably for the best anyways (evan as a clean install my Windows 7 virtual machine is at least 2GB bigger than my existing Windows XP virtual machine). You may have to jump through a few hoops if you purchased Windows 7 as an upgrade to do a clean install on a new virtual machine. The catch is with activation (Microsoft is a little vague on how you are supposed to upgrade from Windows XP to Windows 7). I followed the steps suggested by "morrispe" in this thread and it worked very smoothly. I decided to try the 64 bit version of Windows 7 and it seems to be working without any problems. When you set up your virtual machine, remember that your network configuration needs to be set to "bridge mode" (the default is "NAT mode") in order to sync with Dive Log on iPhone. This is necessary because Bonjour (the Zero-administration networking configuration used by Diving Log 5.0 and Dive Log on iPhone) requires that both devices be on the same subnet. You can change this setting at any time and VMWare Fusion will remind you that you should install the included security software (which you should do regardless of your networking mode in my opinion) if you are going to run in bridge networking mode. Also, depending on how you set up your firewall configuration you may need to enable Diving Log and/or Bonjour to communicate on your network.
You will also need to install either Bonjour for Windows or iTunes into your virtual machine for Diving Log and Dive Log on iPhone to rendezvous. Since you probably use iTunes on your Mac already, you can just install Bonjour and save some space. If you installed the 64 bit version of Windows, you should install the 64 bit version of Bonjour for Windows (the link is on the Bonjour page, but here is the direct link to the x64 bit download). By the way, if you want to by pass Bonjour and establish you link manually you can do that using the steps in this tutorial.
You can install Diving Log 5.0 beta into your new virtual machine by downloading it from http://www.scuba-divelog.com/dl50. You don't need to install Dive Log 4.0 first (unless you want to) as you can just apply your 4.0 registration data to this build (press "r" in the info dialog). Your existing logbook data from Diving Log 4.0 will work with the 5.0 beta release.
I was able to import my Suunto D9 directly into Diving Log 5.0 under Windows 7 on VMWare 3.0. Once your cable is plugged into your Mac, you'll need to enable it in the virtual machine for Windows to use. If you are using the Suunto cable, you will get a message that Windows was unable to find a driver for this device at this point (no worries). You can download the appropriate driver from Suunto's website here. You could install the full Suunto Dive Manager release, but I choose to install just the USB driver (they are listed at the bottom of the page as being for "Suunto t6, G6, X9i, Dive Computers"). You'll want the appropriate driver for your Windows 7 install, either the 64 bit driver or the 32 bit driver. After you run the driver install application you should get all the appropriate "happy sounds" from Windows and your Suunto cable should be available as a COM port (probably COM3). You can always look in the Windows device manager to see which COM port the Suunto cable was assigned to. You should now be able to proceed with importing your dive computer into Diving Log 5.0.
VMWare 3.0 provides some pretty nice interface touches that makes Unity mode much easier to use (check out the new VMWare icon on the status bar). VMWare 3.0 also let you use all the new "Aero" UI features of Windows 7 if you are so inclined.
Diving Log 5.0 beta is looking great! There is a new version of Dive Log for iPhone that has already been submitted to Apple for review that will be able to take advantage of some of the new features in Diving Log 5.0. Keep an eye out for some more posts with information about the new version of Dive Log for iPhone.