As far as weight, the rule states that "passengers in all classes of service are allowed to take into the cabin one article of unchecked baggage weighing up to 10kg forming part of their total free baggage allowance." That is a bit different than U.S. standards or practice anyway as checked weight is 50/70lbs and carry ons are considered seperate. My experience varies greatly from airport to airport. For example, from OVB to SVO, I've never even had my carry-ons weighed. At SVO1, unless I am checking a lot of baggage, inevitable when traveling with my wife and 3 children, they pretty much always ask if I have carry ons though they don't peek over the counter. At SVO2 when flying internationally, they actually stand up, look over the counter and demand that everything gets put on the scale. Just 1 kg over is charged and must be paid for the checked pieces. Generally, my experience is when checking baggage that goes over the allowed limit, carry-ons are no problem. They seem to focus more on the amount due to be paid. If you can get it on the plane though you'll never have to gate check it. They'll stack it in the emergency row before gate checking it. I've seen LOTS of big bags on flights that somehow get put somewhere.

Overhead space during the winter is hard to come by as coats and hats rule the day. All the TUs have smaller overheads that the U.S. standard. The Airbus and Boeings though are plenty roomy.

Basically, its pretty tough to predict as it varies from station to station. I've been shocked (good and bad) over the years at what has been allowed and what has not.