I've taken the Badger Bus between Madison and MKE more times than I can count. Service is friendly, on time--clean buses and always a bonus when you get the double decker. The online purchasing is easy and setting up a account can save you time and money. All buses have wifi but it's pretty slow and unreliable. Definitely an affordable, relaxed way to get to Milwaukee if driving isn't an option.
Tip: there are different schedules leaving from Kelley's Market and the Chazen/Union. When searching online for a bus that works with your schedule, search by town, not by specific stop