Smart trainer + Zwift finally made the indoor setup work for me. I really enjoy indoor training now, whereas I never really got on with exercise bikes and rollers etc. I also use other cycling apps alongside Zwift, like Rouvy (for high quality video routes) and Sufferfest for hardcore structured training. I come out of winter training in top form now with this setup. I might not ride outdoors for 3 months over the winter and then start smashing PBs in the spring. It's that effective! It's not just for winter training either. Often I can get a higher quality structured workout indoors or simulate something I simply can't do locally outside e.g. a 20 km alpine climb. Typically I might do 2 or 3 indoor training rides during the week and longer outdoor rides at the weekend when I have more time.
Some good setup advice on this thread too. You will sweat a LOT! Fans and towels are essential. Check out DC Rainmaker reviews for smart trainer hardware and setup - so many options out there now. Start with Zwift for software.
My indoor setup is pretty simple: Elite Direto X smart trainer + road bike + large fan + iMac + Zwift/Rouvy/SUF