I used it when I started as it was all I could get locally. By the time the tank was cycled I moved away from it. Every time I bought a box the stuff was basically a solid lump despite being sealed, and was pretty hard to dissolve. I wound up using the left overs in holding tubs full of live rock waiting for my current system to built.
The end result actually looks like AquaOne salt too - there's something about the water that just looks Aqua One. A couple of local places have done marine in the past, and there's just something that floats around in the water that tells me it's AquaOne.... and that's really not a good thing. Couldn't bring myself to put it in a tank now if you paid me!
You can changes salts - just be weary that different salts can result in variations to their makeup - some are higher in certain elements than others. Red Sea Coral Pro for example is a mix that has specific elements more targeted towards reef tanks. The AquaOne salt... not so much. It's not the end of the world, but some of those missing elements may be beneficial to your tank (depending on its contents).
I wound up using Red Sea Coral Pro until I stopped using ASW, and it is by far the superior product compared to AquaOne. There are certainly some cheaper salts out there than the Red Sea stuff, and most of them are likely to be better than AquaOne. Salts do vary, and peoples experiences vary wildly with them. Personally, I have found though that the more expensive salts I've used were typically the easiest to mix and came out looking clean rather than full of visible particles floating around my tank. My first non-Aqua One salt was Aquasonic... it was by no means cheap, but it mixed very easily and was quite clean. I then moved to a brand I can't remember beyond it being imported from Japan which was cheap and was really easy to mix and clean... then finally on to the Red Sea Coral Pro. That's when I started getting a lot of improved growth in the tank, and things started to settle.
In the middle of that I'd bought some Tetra Marine Pro salt that was on special - I think I bought about 20kg of it. Half of it was a solid lump, it took days to get it to mix, and it left a huge amount of residue in the mixing tank. There were also quite a lot of particles floating in the water. Nearly all of this was used in holding tanks like my left over Aquaone salt was (I had live rock and sand in holding containers for months!). There is a thread here somewhere about using this particular salt!
Edit: I'd also be weary of any salt thats instructions condone using tap water in the mix without any logical warnings against such a thing. That stuff is a little too eager to tell you to just use tap water... and it's information on salinities if I recall were a little bit on the way too low for a reef system.
So, in case that was too long to read: Personally, I'd be sticking with the Red Sea Coral Pro, or at least look for a salt that you can find out some positive feedback for... and perhaps has the elements in the mix listed on the container :)
