I have the Daysafe 100 and I really like it.
It has the zip-out sleeve with the integrated cable lock. You can leave that zipped in, and run the lock out through a purpose-built hole in the top, but I usually leave that part in my hotel room with things like passports, cell-phones, etc... locked safely away. The rest of the bag is very roomy and carries more than enough (2 jackets, H2O, travel books, iPods, camera) for a day of sightseeing for my wife and me. I am using it for a carry-on on my upcoming trip, and it easily holds 2 reg bags, plus a book, magazines, snacks, etc...
PLUS, it is also slash resistant, snatch resistant (the shoulder straps are cable-reinforced) and it has nifty little snap links that hold the zippers shut and tuck away to where they are easy enough for me to open, but would present a pickpocket with a challenge.
I am thinking about getting a smaller one (messenger bag style) for travel when I don't need to carry as much, but the zip-out "safe" portion will still come along in my checked bag.
Comes with a keyed padlock, which I trashed and instead use a TSA lock off my checked bag once I am unpacked.
-Jim