I'm a rank beginner here, so not sure how valuable my input is. I bought my bike specifically to commute ten miles each way to work. I was going to buy a scooter, but for any scooter of at least 250cc the price way about 4,000$. I just happened to find a one owner 78 750K that had been meticulously cared for, for 1600$.
It seemed too big and has hardly any rain protectiion (does have a clear windsheild), but I'm getting used to it and it runs really well, smooth, plenty of power. I did have to spend a bunch of money to get outfitted for dryness, warmth, and enhanced visibility.
I've had to ride a few times in the rain, and it wasn't bad. I have had some problems when we are socked in with fog; windshield, mirrors, facesheild on helmet, and glasses all totally fogged over. I'm on the Pacific Northwest Coast.
My 750K is probably far from a perfect commuter, but it's reliable, plenty powerful for the highway at 60-70mph, and for passing. One thing that i think would make it better would be for more, larger, and brighter running lights.
My bike is in very good shape and I figure I just should just use it, it should go for many more miles. If it was in mint condition, I don't think I would do this but probably try and sell it to someone who could appreciate it as a classic bike and get something else to use to commute with. But buying something else in the price range I can afford is probably a real crap shoot. I've got a great bike, might as well just use it.