Personally, I am an enormous fan of both meters. I think that both present a decent challenge for players that the Zelda series never really offered previously. Skyward Sword is definitely made better by these two items; not only does it make it more realistic, but it also adds a bit more challenge to the game itself. Normally Zelda just utilizes puzzles, but now you have to keep more than just the area around you in mind. Aside from just that, it adds more necessity to your wallet. Before, you bought a lot until the middle of the game, but in Skyward Sword, you may have to fix your shield constantly, adding more use to each precious rupee you collect.
Now, the shield meter was never really that big of a problem for me. I've never really used the shield constantly because I normally play more of the offensive role than defensive, and this is the same in every single game I play. The shield's durability even at its weakest form was fine for me, but I still constantly upgrade them just to get maximum use out of my shields. I think the closest to breaking my shield had ever been was about halfway when I tried to shield bash Ghirahim, but instead just blocked his attack. I feel the shield is an important item, but I doubt I'm ever going to truly need it desperately like I see in some gameplay videos. Besides, once you receive the sacred shield (or the Hylian shield) it's quite difficult to break them - breaking the Hylian shield is impossible - because the sacred shields just regenerate. And now that I think about it, the Hylian Shield doesn't break in Skyward Sword, exactly like it doesn't in all the other Zelda games. Exactly like in Skyward Sword, the wooden shields can break, but only when it's being heated. I can only guess that the Hylian Shield has some magic or the Goddess's blessing that make it indestructible.
Definitely I used the stamina meter a lot more than the shield meter - it was required. It's a lot easier to run out of stamina than it is to break your shield, but that's to be expected. I've never really had much of a problem with the stamina meter per se, I've just squandered it and drown in the quicksand, or run straight into enemy territory and then run out of breath right as I'm the center of attention. If not for the stamina meter, half of the Lanayru Mining Facility dungeon would be very easy; getting to the actual dungeon would also be significantly easier. Without the stamina meter, entire parts of the game wouldn't be difficult, so even though it was a bit of a bother to have, it really affected the game itself. Without these two meters, the game would be noticeably easier.