Just back from a trip to Chile and ended with four days in Vina del Mar. Some quick thoughts:
Transfers: We flew into SCL (returning from Patagonia) and used Uber Black from the airport to our hotel. Apparently Uber is still controversial in Chile as our driver (a very nice young woman) phoned and asked us to meet in the parking area and to greet her as if she were a friend, kisses and hugs, and then sit in the front seat as she left the airport area. Other than that small weirdness, was efficient and approximately USD $120 for an hour and a half, 100 km trip in an upscale car. On our return we had our hotel arrange a car and driver (the Sheraton Miramar) and we paid approx. $170 for a Mercedes van and a driver in a dark suit.
Hotel: stayed at the Sheraton Miramar. Lots of information on the Sheraton board here and on trip*advisor - I'll put a review there eventually. Solid, 3-Star business-class hotel, OK restaurants and bar. Great gym and spa area. Fantastic views. A bit isolated due to the location but probably quieter because of that - only a ten minute walk into Vina, and less than that to a Metro stop.
Vina vs. Valpo - did walking tours in both towns and also went into Vina on our own a few times. Yes, Vina is cleaner in general than Valpo but both have trash, graffiti and stray dogs (friendly stray dogs as everywhere in Chile!). Vina has more of a vacation feel and Valpo is a working city.
Tours: we used Tours 4 Tips in each town; actually ended up with the same guide for both tours. They have a great process and give good tours, highly recommend them unless you have mobility problems. Also arranged a half-day wine tasting tour in Casablanca with lunch through Al Ramirez tours, also recommend them. We got the pass for the train/metro and used it on our own to explore a bit and never felt unsafe but we were only out in the day time. Visited the Fonck museum which is a little gem - fascinating displays on Easter Island and also on the indigenous people of Chile - we happened to be there when an English speaking guide was available and she gave us a perfect 45-minute overview.