From what I've observed, the name taken at Chrismation is used only within the Church, and even then, only at communion. It's also common for someone to take a patron saint who shares their name, if they already have a saint's name, so there's not much change for them. Some take entirely different saints, though, and those who don't have a saint's name already take one. Actual usage and practice varies, however. For example, my given name is Benjamin. Since I'm of Russian descent and have an affinity for martyrs for some reason, I chose St. Veniamin of Petrograd as my patron, which simply gave me the Russian form of my name. For the most part, the English form is what's used in daily use, but the Russian does get used every once in a while. It really does vary from person to person and among jurisdictions and parishes as well, from what I've observed. As a practical matter, when you take a saint's name, you probably won't be using that all the time unless you just really want to, so you don't have to feel like it's replacing one of your given names.