I handled a few of the early ones. They may have improved since I handled them...
But, honestly, I was not that impressed.
First, the vesuvius is too small for my tastes. Somehow, I expected it to be bigger. The delica seems like much more of a handfull.
I like the compression lock. It's a cool lock, very strong and simple.
But, it doesn't seem to have very positive lockup when closed. In my gunting, this was a bit of a problem, as it would come open easily if the pivot pin was ever-so-slightly out of adjustment. I have heard many stories of the vesuvius coming open in the pocket. Makes me nervous. When I opened the vesuvius, it had the feel of liner lock that has lost its ball detent; smooth, but... not right, somehow.
This could have been fixed on the newer models. Spyderco is always working to improve things. Even the delica and native are subject to change and improvement.
Also, the fit, finish, and quality just didn't seem up to par. I didn't particularily like the inlay, either.
One of my current EDC rotation knives, the Lil temperance, also has the compression lock. It seems to be a vast improvement over the early guntings and vesuvius's (vesuvii?). I like the lil temperance a lot. I can't recommend it enough.
Anyways, you may want to handle the vesuvius before you buy, if possible. I nearly bought one over the internet. Fortunately, I handled it first.
I'm a big fan of Spyderco. I've purchased many of their knives. I have to say, though, that the vesuvius is probably not one of their best.
Just my $.02
-- Rob