Are you sure that fgetl is what's taking the time? Or are you trying to read data one line at a time from a file and storing each line in turn in a cell array, and if so is growing the cell array the bottleneck? Can you show a bit of context for your fgetl call?
If you just want to read in data all at once, try fileread. You'd need to split it into its constitutent lines if you wanted to process a line at a time, but at least you'd only perform file I/O once.
t = fileread('bench.dat');