The only significant drawback to the Echo II System is the small size of its Tarp, which is less protective and less comfortable than the average two-person flat or A-frame tarp we've tested. It performs relatively poorly when used without the Beak or Insert because its short, curved walls become very steep when you pitch it close to the ground, or the peak is very low, resulting in little room to sit up. Our tests show that the increased comfort of larger A-frame tarps (like the Mountain Laurel Designs Grace Tarp Duo) or square flat tarps provide much more comfort and weather protection when used without an insert, and they weigh as little as one ounce more. When traveling with two people we almost always bring the entire Echo II System; the shelter's modularity is more useful in theory than in practice. Because of this drawback, our scoring assesses the Echo II when used with all components. Then, the tent performs better than any dedicated pole supported backpacking tent we've tested (for ultralight backpacking), but not as well as some other "world's best" ultralight shelters.
If you want the most versatile and lightest shelter consider the Hyperlite Mountain Gear Square Flat Tarp, which is much more comfortable, more versatile, and more weather resistant than HMG's Echo II Tarp.
If you want the lightest possible high functioning tent with bug protection, the ZPacks Hexamid Twin Tent is the best we've tested. Check out our comprehensive Ultralight Tent Review to compare all of the models described here, and others.