I don't normally write reviews however I am more than happy to offer one for this product.
I recently bought the Hardside Hydration system and "upsized" to the full kit complete with 1.5litre Nalgene bottle and neoprene sleeve. Not cheap at just over $100 but, given that it solves a big problem for me, I don't begrudge the cost.
I love hydration bladders and they work well for day packs however I find them cumbersome for multi-day backpacking walks. They take up a lot of space, are difficult to remove to refill when your pack is full and don't pour well for use around camp. Instead I carry water in bottles but I find them very hard to access from the side pockets of a backpack when walking so, consequently, I usually don't drink enough.
The Hardside system solves this. I can now carry 1.5 litres conveniently and driink on the go. If I need more water I simply carry another litre or so in another Nalgene and transfer the water to the Hardside system when I stop for a break.
In the short time I have owned this system I have used in extensively on both day walks and a multi day walks in the Grampians. It works a treat and I would highly recommend.