I have a
Fitbit Force (recently
recalled due to skin rashes). I really like the numeric display on the Force as opposed to the dots on the Flex.
Fitbit has a pretty cool online dashboard and app. Both the Force and Flex only sync to certain phones that have Bluetooth 4. If you can't use your phone you have to use a miniscule wireless USB dongle on your computer. My Macbook Pro only has 2 USB ports, so it's really inconvenient to have it plugged in and really easy to misplace.
To track sleep you have to indicate when you go to sleep by pushing a button when you lay down and doing the same when you wake up. If you forget, you can enter the sleep and wake times on the dashboard and it will fill in the activity.
It doesn't track activity that does not involve steps (i.e. weightlifting or yoga) but you can track the time using the same procedure as the sleep timer.