Our friends over at Download Squad reviewed Calgoo, an offline Google Calendar client, last month. The reason we didn't pick it up is simply because it didn't run on Mac OS X at the time. Recently that changed, so here we go - but it is very apparent why they call this a first draft (as opposed to 'beta' or even 'pre-alpha').
Calgoo appears to be a Java app, or at least need it for something under the hood, and as you can see: it isn't quite on the Mac OS X side of the GUI fence. For some odd reason, users must register at Calgoo's site (which I begrudgingly did in the name of blogging) in order to be able to download and actually use the app. The actual setup is pretty straight forward, and syncing seemed to run well (a 'Message Log' tab in the upper right lets you keep an eye on activity), but navigating Calgoo's UI is anything but intuitive. Like Jason at Download Squad, I too couldn't see any of my appointments until I figured out their obscure calendar list in the lower left corner (hint: you can select and view individual calendars, or click at the top of the list to view them all. Why it's an actual process to get even any of your calendars to appear is anyone's guess). There are various other quirks and perks, such as Calgoo running on Mac, PC and Linux, event tagging/filtering and the fact that it downloads your Gmail buddies for easy attendance listing, but I was happy to see what is perhaps the most significant feature of Calgoo work like a charm: syncing with Google Calendar. I created a couple basic events in Calgoo and one in gCal, then synced. Once the dust settled, everything was reassuringly in order across both places, so at least that's a good selling point at this 'first draft' stage - cuz that UI sure won't be winning any Apple Design Awards anytime soon.
So would I recommend Calgoo? Yes and no. If you're just gaga for gCal, sure - it seems like a decent client, but there's definitely a UI learning curve. However, this seems to be the only app I've seen that has put a good foot forward in accomplishing such a task as truly synchronizing with Google Calendar, so I'll tip my hat to Calgoo and hope to see what tidings its evolution brings.