Vodafone's attempted solution to its year of poor performance is a bunch of network upgrades around the country. A tool on its site lets you check what works have been completed or are planned in your area, as well as identifying current performance issues.
Throw your postcode into the tool and you'll see what work is completed and planned. It's pretty evident that Vodafone saying that it has completed upgrades doesn't always translate into better performance, and I suspect many people are taking a "once burned, twice shy" approach to the company. However, if you are contemplating a Vodafone option, it's definitely worth checking the site first across any locations you regularly visit.