Wow. Someone hand me a cigarette. Just got back from a ride using the Giant Loop Great Basin Saddlebag (http://www.giantloopmoto.com/)and the experience was that fulfilling.
At first glance the bag is a bit of a concern for a rider who's been using strictly hardbags. But let me tell you, the Great Basin is a rider's dream. The mounting is done in a quick and easy manner simply by looping the 5 straps around a point on the bike and pushing the strap through the fastener. Easy Peasy. The "U" shape of the bag allows it conform nicely on the rear seat and yet hang at an angle which didn't affect my riding. Their website touts "rides like it's not even there" and well, they aren't kidding. I had to turn around to make sure the bag hadn't fallen off.
Probably the best part is the weight of the Great Basin. Coming in at 50 liter volume and having an empty weight of only 8 pounds (on my home scale) the bag is light and has enough capacity for a day ride, commuting for work and even a weekend trip. And, it's light enough that even a child can lift it, carry it, and maneuver the bag without an issue.
The width of the bag when on the bike was about 29" as compared to my hardcases which are about 40" wide. The Great Basin has compression straps on the side so the width can change, and even when not completely full there isn't flapping in the wind due to the location of the straps and the compression ability. And speaking of flapping, not an issue in the world with drag, which is a common thing with my huge hardcase panniers.
I had the bag fully strapped onto the bike and realized I'd forgotten to put my purse in for my test ride. There was no problem with opening the zipper and just pushing it in because the zipper runs far enough down the edge of the bag to enable access. The zippers are strong and durable which is a good thing considering on most my gear the zippers break first.
Per Giant Loop's website the bag is made of waterproof material but the seams need to be sealed. This isn't a problem for some riders as their bikes are stationary until the rain stops. I ride all year round but I welcome the opportunity to test the bag in the weather.
My only real concern with the bag, given my type of riding, is security. In the set up I currently have the bags are locked to the bike and have locks keeping everything inside secure. The peace of mind I get from that is a big bonus. With the Great Basin there is essentially no security. Sure, you could use a Pacsafe but that's an extra expense. Of course, even with the extra expense of a Pacsafe anti theft system the Great Basin comes in at a reasonable price of only $399. That's less than a quarter of what I paid for the hardcases. A lot less.
Overall the Giant Loop Great Basin bag is a winner. I'd use it and I'd love it. Now about a tank bag....