I've done 4 weekend hikes this spring/early summer that could be classified as SUL, with a base weight below 5 pounds.
Key has been to reduce the number of gear items to a minimum, skipping kitchen and using a poncho-tarp setup with down top bag & small inflatable matress.
I've definately enjoyed it, the hiking is more fun, I can occationally run when I feel like it, making and breaking camp is quick and easy. The less gear I bring, the more freedom and connection with my surroundings I feel. The gear list has basically been:
*Tooth-brush & paste
(+wallet, keys, bus pass)
Worn were thin softshell trousers and thin soft shell jacket, cap, t-shirt, underwear, socks, trail runnning shoes, Katadhin filter bottle in pouch on belt.
The pack is only 1000 cu in, so it is also essential to have compact, high-energy food. A thin foam mat can be a lot lighter than a TR Prolite 3 matress, but takes up too much space.
But this has been easy on low-land trails. Doing the same when hiking in the mountains will be much more of a challenge, but I'll give it a go this summer.