Great plugin! I love the idea, but unfortunately it doesn't work with tabs. Looks like it's because when using | to jump to a column, it uses screen columns (instead of actual columns -- see :help bar). Maybe you could multiply the number of tab characters by the value of tabstop?

Repro:
Edit word-column.vim
Put cursor on first 'let' in file.
vic selects all of the lets.
%sm/^ /\t to switch to tabs.
Put cursor on first 'let' in file.
vic selects some weird stuff (on ca711dd it selects a bunch of stuff late in the file and on 69c30da it selects from the beginning of the line).