There is much to like about the Buck Sirius. I have both the 420HC and the ATS34 versions. It's a well-made, fast-opening, solid-locking, sharp-as-dickens general purpose knife. I was so impressed with it, that I also bought one for my son and had it signed and engraved with his name.
However, as I tried to work it into my EDC rotation, I just kept finding it less than optimum.
Unhappily, it's just a little too heavy to carry EDC, it's just a bit too thick for a lot of my everyday stuff (like making a salad or slicing cheese), the liner lock has a weird (and painful) sawtooth ripple right where you have to press on it with your thumb, and there's a cam-lock lever right there I want to put my thumb on the spine.
Now, Sirius has a little brother, the Rush, that is essentially a scaled down version of the Sirius, but the change in size makes all the difference. The Rush is light and handy, the cam-lock tab is still on the back, but its placement somehow doesn't interfere with my grip, the blade thickness is fine for most of what I do, the very pointy point is awesome for package and box opening. It has the same sawtooth ripple on the liner lock, but it doesn't hurt my thumb.
So, even though the Rush and Sirius are the "same" knife in two different sizes, I really like the Rush, and I've never been able to warm to the Sirius.
Don't get me wrong, though. It's not like I'm gonna just "dispose" of the pair of Sirius examples I have. Yeah, I might sell them, but not cheap. Heck, I could maybe get enough from selling them to afford another Paradigm.