We have had a Food Saver for several years and never found the canisters cumbersome to use and not very useful. We also don't use very many of their expensive rolls of bags, except for frozen meat. However, I keep the Food Saver out on the counter and use it several times a week to reseal everything from potato chip bags, most of the bags that frozen vegetables come in, the bags that chocolate chips come in, and several other similar things. It's not suitable for the softer poly bags, such as bread wrappers, but anything that is made of the mylar type plastics works great, as well as the type that line cereal and cracker boxes. I didn't think I needed this machine until a friend gave us his extra because he was upgrading to a newer one. I would really miss it if we didn't have it now! It makes a much better seal than twisties and clips.
By the way, I'm not using the vacuum function with those types of bags and wouldn't expect it to work except with their specially designed products. Certainly there is a use for those things, too. I've heard that you can even use them to vacuum seal fabric for long term storage, but I haven't tried that. I'd have to leave a lot of headroom for resealing because just as soon as I got something packed away I'd find a use for it!
One other use is repairing the holes that often occur in grocery bags. I know we're supposed to not get those bags, but what else would I be using for cat litter gleanings and doggy pick-ups and to line bathroom wastebaskets? I like re-purposing the bags, but obviously holes would not be good, and more than half of them seem to come with holes. I see people buying plastic bags for this kind of thing and carrying them home in lovely fabric totes, and I wonder how that could be any more environmentally friendly than what I do.