I can’t tell you how many Subversion users have told me the following story: “We tried to branch our code, and that worked fine. But when it came time to merge back, it was a complete nightmare and we had to practically reapply every change by hand, and we swore never again and we developed a new way of developing software using if statements instead of branches.”
Joel Spolsky (die gezegd had dat hij niet meer ging bloggen?) in zijn laatste blogpost over version control.