Please note: CalenGoo is a universal (iPad + iPhone) app; however, this review is based on the iPhone version. Both are included with your purchase.
CalenGoo is a (unofficial) Google Calendar app for the iPhone. At first glance, the built-in Calendar app with its Google sync seems to make such an app superfluous. However, if you're a power user of Google Calendar, you'll definitely appreciate CalenGoo. It's hard to beat an app that's so tightly integrated with the Google services we all know and love.
To use CalenGoo, you'll first need to set up synchronization with your Google account. You can sync all of your events, or just recent and future ones; you can chose which calendars to sync, if you manage multiples; and you can even sync (and manage!) your Tasks.
Now onto using it! CalenGoo lets you view your events in almost any way you want: by month, week, or day; horizontally or vertically, it's your choice. The interface mimics the web version and preserves your color-coding. You can also attach icons to events, which is plenty of fun.
Editing events? Yup, you can do that. Setting alerts? Uh-huh, though Google handles them. A Jump-To-Date button makes navigation easy. Adding events is simple as well; you can add the usual time/date/notes, but the feature I like best is "location"—CalenGoo integrates the location with the default Maps app, showing you where you need to go. I haven't had any problems with syncing, and the app works offline.
As far as complaints, it's hard to find any. CalenGoo functions much as you would expect. If I had to pick one complaint, it's that short events are hard to select by tapping on them, and the interface in general feels a bit cramped. But really, pinch-to-zoom solves the first problem and the second isn't too important.
All in all, if you're a power user of Google Calender—you juggle multiple calendars, you rely on it to tell you where to go—this is the one to get. CalenGoo is a huge step up from the default Calendar app, and much better than any other Google Calendar app I've seen. The syncing is great, offline access is a savior, and the app's flexibility and ever-growing feature list make it better still. CalenGoo might have a funny name, but it's dead serious in terms of raw, powerful function.