I have a standard 510 riva and an eGo T atty and t-carts, all from Liberty-Flights. The eGo tank is great! It is the best system I have found in my short time vaping. I will say there has been some struggles with cleaning on my end, but that is user error and a lack of experience on my part.
I love the setup and I can't say enough about it. I'm ordering 3 more attys and 10 carts come payday!
The method I use for filling is just popping off the small end cap on the cartridge (atty end) and just drip into the tank until it is 80% full, pop the cap back on, snap it into the atty and you are ready to rock and roll for 1ml. No leaking, no problems.
I will say they seem to use a bit more juice than the cartos I was using, but the great vapor production and taste make that absolutely worth it in my opinion. The difference really isn't much but expect to use just a tad more juice.
Hope that helps! But as always, ymmv!