Have to disagree. It depends on what you are doing. That the alternatives can be replacements, including the open source ones, is relative and should be looked at as a percentage.

If you listed out all the things that Excel can do, we might find that the alternative is at 80% or so (just a number), with some additional things that Excel can't do. That 80% could be good enough to switch. It should not be looked at as "all or nothing", especially for every person or business.