It actually is a surprisingly diverse in its appeal.
I bought mine for $310 with the intention of leaving it bone stock, as I wanted an inexpensive gun that could go anywhere with me and still provide a useful amount of firepower. I don't like the small plastic semiautomatic pistols to be had around this same price point. I did have to change the grips however.
However with some gunsmith work and accessories, it could be something altogether different.
I think the Ultimate BUG is probably the R9, but it costs 3 times as much as the 642, and even if you tricked your 642 out the R9 still costs a lot more. No disrespect to this or any other gun is intended, but it's not worth that kind of money to me for such a dimunuitive (sp) amount of firepower.
However, considering most of us settle on a single action or DA/SA semiauto for our primary, a DAO revolver makes a lot of sense for a BUG. A lot of us, myself included, are revolver lovers and will always feel better armed having one available. If nothing else, we can all appreciate that both formats offer clear and distinct advantages so carrying both makes a lot of sense.
One thing I've heard of recently with some other pocket type guns like the PM9 is that while the gun itself is of excellent quality, the Achilles heel is that often a basic control like the magazine release can be depressed in pocket carry. Now obviously not everyone experiences this problem, but I can see something like that happening.
The way I look at it, 2 COM shots at social distances even without using the sights is a realistic goal with the 642, and I don't care who you are, that's going to ruin your day when you're on the wrong end of it.
Not to mention I've perused some materials myself which discuss the role of small handguns in extreme CQC, and the snubnose revolver is a consistent winner. The police have been using them in this regard for decades now in both on and off duty carry, and when it comes to practical firearms and their application, patrol officers wrote the book.
I personally want to digest this book sometime: