I just recently was working on a site what had its fonts set like so: 

1. h1 {
2. font-size: 4vw;
3. }
4. 
   
5. h2 {
6. font-size: 3vw;
7. }
8. 
   
9. p {
10. font-size: 1.5vw;
11. }

Now i noticed a few issues with this approach:

- The fonts unlike em's , rems and fixed width units like px , scale based on viewwpoints , now thats great , but has a huge drawback ,

  the fonts that look good at 992px will scale to be so tiny at 448px width that they would hardly be visible. 

- If you were hypothetically working for a design company where the fonts size of the site has to be pixel perfect and say the h1 size of your design is 35px ,

  how the heck on earth are you going to say 4vw = 35px ? is it possible to accomplish pixel perfection with vw, vh and company ? With em's you still can cofidently 

  code yor font sizes and know that they won't suddenly become tiny or will atleast be of a certain size. the below strategy has often worked for me.

1. body {
2. font-size: 16px;
3. }
4. 
   
5. h1 {
6. font-size: 3em
7. }
8. 
   
9. .bigFont {
10.     font-size: 1.56em;
11. }

the above code gives me close to pixel perfection , Now i know setting body to 100% is whats ideal , Unfortunatly i don't have the luxury of doing that ;) 

can i acheive something like the above with vw , vh and company ?? or where these units just not created to deal with situations like above ? 

Also one critical downfall i noticed with using such font sizes is that , multiple viewpoints they look completely different, hence i have to use 

multiple media queries. so using such units kind of becomes counter productive . 

1. h1 {
2. font-size: 4vw;
3. }
4. 
   
5. h2 {
6. font-size: 3vw;
7. }
8. 
   
9. p {
10. font-size: 1.5vw;
11. }
12. 
    
13. @media (max-width: 992px) {
15. // set font sizes for h1 , h2 , p and so on again Here .....................
16. 
    
17. }
18. 
    
19. 
    
20. @media (max-width: 768px) {
22. // set font sizes for h1 , h2 , p and so on again Here .....................
23. 
    
24. }
25. 
    
26. 
    
27. @media (max-width: 448px) {
29. // set font sizes for h1 , h2 , p and so on again Here .....................
30. 
    
31. }

Now the irony is that even after you've done the above you're still not garuinteed that you're font size will be the size you what it to be at a given viewpoint. 

All of the above make me kind of rethink if vm and co. were actually added to CSS to set fontsizes or where they invented for other purposes . 

I have no idea. can somebody please tell me then what would be the use cases for vw and co. ? 

P.S.: i know this is a jQuey forum , but just taught i'd post it here in case somebody has extensively used vw's in their projects.