I have the older version of the GIVI combination roller bag top case. It snaps onto the same rack as my GIVI hard case.
I commute between Portland, OR and SF, CA at least once every two months for most of the year and have used this unit, as it caries my lap top and other office stuff safely, and doubles as a roller bag/briefcase. it is one of my favorite pieces of equipment. I have the first model that GIVI made, and have not replaced it with the much improved new model because it is still in nearly perfect condition after almost 3 years. It comes with a rain cover, but even though I often ride in inclement Pacific NW weather during this long commute, I have had zero leakage problem and only put on the rain cover when it is really pouring. It is not as big as the larger hard cases, but works just fine for both the computer/office stuff and that other things I usually put into the top box like my alternate gloves, heated gear and other things I need access to during a long ride through changeable weather-most of the time actually, on the NW coast.
Once I get to my office location in SF, the roller bag is a convenient, very presentable and useful, roller bag brief case with plenty of room for everything I need for doing business.
Having the combination of the stock panniers, an E52 hard top case for non biz travel, and the roller bag case for biz travel use-that fit, and lock, onto the same rack works for everything I need.
the GIVI roller bag/top case is very useful item. I recommend it.