I highly recommend the SW-Motech mount and Bags Connection bags. They have a system that includes a wide variety of mounts for various motorcycles, tank bags, and accessories. If you are looking for the highest quality, most durable, most useable, most flexible tank bag system, this is it. All of the SW-Motech Bags Connection bags (that I know of) come with a hidden zipper pocket with a rain cover, too.
The tank bags snap into the tank rings with a solid click. The latch is strong and reassuring. I have never had a bag disconnect while riding - the thought is almost laughable. (I can't say that about the old magnetic tank bags that I had for my old Honda Magna!)
The bags do not touch your tank. The mount holds the bag firmly about 1/4 inch above it. A hidden cord is used to pull the spring loaded pin (or pins) to unlatch the bag in one step. It cannot happen accidentally. I remove the tank bag without thinking - just reach behind, pull the cord, and lift the tank bag by the handle. I do it in one motion.
In addition to the bags, you can buy other accessories that fit in the mount or on the bags themselves. I have the simple map pocket - which fits on all the bags. There are GPS mounts that fit on the bags, camera mounts, RAM mounts (which connect to anything), etc. etc. etc.
I have ridden with my favorite Engage bag for many years and tens of thousands of miles. Despite the wear and tear, it looks almost new, with perhaps a little sun fading over the years.
Here are a few things that I have learned about SW-Motech mounts and bags:
There are two types of SW-Motech mount fittings, the current "EVO" (recommended) and the older "ION" (obsolete, sold for those who need compatibility with an old system). Furthermore, you can divide each EVO or ION mount into electrical and non-electrical versions. The electrical versions have contact pads which bring electric power from your motorcycle to the tank bag for charging cell phones and other devices, convenience lighting (they sell a lighted map pocket, for example), etc.
The part that goes on the motorcycle is called a "tank ring." You will need one of these for each motorcycle. Before you start, make sure that tank rings are available for the all the motorcycles that you own.
The part that goes under the bag is called the "top ring." You will need one of these for each tank bag.
The tank rings and top rings come in electrical and non-electrical versions. If you are going electrical (recommended!), make sure that all rings are electrical - tank rings and top rings. A non-electrical top ring will snap into a electrical tank ring and visa versa, but obviously the electricity won't be available in the tank bag.
In case anyone cares, I am switching from my old, non-electrical ION mount to the new electrical EVO mount, and have new bags to deploy for longer trips. Those bags will hold more than my old Engage bag.
Good sources to look for SW-Motech in the US are:
Pirates' Lair: Aftermarket, Custom, and Performance Motorcycle Accessories for Exotic Motorcycles
(Try them first, because they have been so supportive of the k-bikes.com and i-bmw.com communities.)
Motorcycle Luggage, Motorcycle Protection, Handguards & Accessories | TwistedThrottle.com
Even though the SW-Motech mounts and Bags Connection bags are expensive, they are so durable and well-designed that they are a true value in the proper sense of the word. When you buy a new motorcycle, just get the new tank ring for it and continue using your bags with it.