More impressive if you look at the actual mph for each category:
F1: 40-72mph
F2: 73-112mph
F3: 112-157mph
F4: 207-260mph
F5: 261-318mph
And, technically there is a F6: 319-379, although these are termed "inconceivable".
Check here for more specific details.
And, yes, I've been through a number of tornados, including F4 & F5. Sort of fun & interesting to watch. 
EDITed to add: Even a few of those "serious" categories while in a trailer. There are some instances when leaving during the midst of a tornado is not the brightest of ideas.