Like you, I didn't use my jig saw very often. It was a Craftsman, probably 40 years old. I only used it for rough cuts since, like yours, the blade went out of vertical on anything more than gentle curves, and it vibrated. About a year ago, Lowe's had a sale and, with my military discount, I couldn't pass it up. Like Oliver, it was almost a biblical experience. I finally found out why they made jig saws. I've used it more in the last year than I did the Craftsman in the last 10 years. Well worth the price. I know how hard it is to part with a tool, especially if it's an old friend, even if you fought with it all the time, but sometimes it's the best move.
If you have an open mind, you’ll generally find that you’ll learn the most from the people who say the things you least want to hear.