I started in mid-2010. My workday starts earlier than most engineers: I take an 0640 shuttle in from the east bay, arriving at my desk around 0715. I typically take the 1655 or 1720 shuttle back home; on rare occasions or when under external deadlines I'll sometimes take the 1810 or 1840 shuttle back home. I almost always leave on the earliest 1605 shuttle on Friday. My day almost always includes a relaxing hour-long lunch with my coworkers.
So at the extreme high end (0640/1840 shuttle), I'm away from my house for about 64 hours a week. Ordinarily (0640/1655 shuttle), I'm away from the house around 55 hours a week. This includes both my lunch and about an hour on the shuttle each day, so depending on whether I work on the shuttle (I almost always do), my actual working hours are 35-45 hours, lunch excluded.
Oftentimes I'll come home and idly hack on work stuff while I'm sitting in my comfy chair and my wife and I watching her shows, but I'm sure exactly how to account for that time. It doesn't feel like work, I'm just hacking on what happens to be the most interesting stuff I could be hacking on at the moment.
It varies a great deal. Each team has a distinctive culture, and there's a lot of individual variation too.
I typically arrive at Google about 9:20 (until recently the breakfast cafeteria at the NYC office closed at 9:30, although that's no longer the case I've kept the habit), but don't really start working until ~10. If I have plans in the evening I'll leave around 6, if not, I'll stay for dinner and keep working until 8-8:30. I've never come in on the weekend.
One coworker on my team is always there before I arrive, and is always still there when I leave, but everyone else on my team floats in gradually until 11:30 (when we have our daily standup), and leaves sometime between 7 and 10.
While some days I may spend 10 hours in the office building, consider that this includes 3 meals and usually at least one other major distraction (a tech talk, a break in the game room, TGIF, or something).
Edit: I've been in the NYC office around 4 months.
Another Aussie Googler in the NYC office? Drop me a line (see my profile).
Personally my schedule varies. Lately I've been getting in between 11 and 1 and staying until dinner (6:30) or later, sometimes very late (midnight+). Not all of that is work time as I often end up hanging out with other night owls.
My team is generally on a more normal schedule. Nearly everyone in the group is gone at or by dinner.
I'm not sure there's such thing as a "typical" work week. I know that even in just my personal experience, there are long weeks, and there are short weeks, depending on the needs of the project at the time.
I have had weeks where I'd get into work around 10:00 AM and work till 1:00 AM on Mon/Tues, till 11:00 PM on Weds, normal hours (about 10:30 AM - 6:30 PM) Thurs/Fri, and then put in about 3-4 hours on Saturday as well.
I've also had weeks - like last week - where I get in at 1:00 PM, do a bunch of code-review threads & meetings, have a launch party, drink some margaritas out on the Charlie's Patio, watch a Starcraft tournament, and go home after dinner at 6:30.
If you have a good manager, their objective will be to have you accomplish a lot of things for Google without burning you out, so that you can continue to accomplish a lot for Google. And the "heavy" weeks I've mentioned above have accomplished a lot for Google - I've made more money for my employer than I am likely to make in my lifetime. As long as I don't spend all my time slacking off, they don't mind if I spend a few mornings on personal stuff and take advantage of the perks at the Googleplex.
