Congratulations on getting back into it. Although never a clyde (not for want of trying, but at 5'-3" it takes more effort than usual to make it to clyde-dom, and even at that I got scarily close), I was 50+ when I started year-round commuting about 2 years ago. You're right, your times will improve (if you want them to), the weight will drop off (assuming you stick to a healthy/sensible diet), and you'll enjoy commuting even more.