My Own White Box Experiences
To date, I've bought nothing but white box desktops, six (plus upgrades) over the past fifteen years, from my local (greater Boston area) shopsMicroSmart, NPC, and PCs for Everyone.
My white box computers have ranged from a DOS 286 with 10MB disk, 4MB RAM, and a 1200-baud modem; through my current AMD 1700 and AMD 1800 Windows 2000 and Windows XP desktops (production and test machines, respectively), each with 1GB RAM and two 60GB hard drives, with an outboard hard drive and CD burner, still using a 15-year-old 17-inch CRT through a KVM switch. The main indulgence for my boxes from PCs for Everyone was nice Lian Li aluminum cases with extra fans. For the most part, I'm doing text processing, email, and web, so most of my power goes to keeping the operating system (OS) peppy.
The 286 cost me either $1,000 or $2,000 (I forget which) back in the late 1980s; my XP desktop ran me slightly over $1,200 or so a year ago, I think. In some cases, I could probably have gotten better prices from Dell, etc., but I've never had regrets. (Well, not about not having bought a mainstream system... I do regret some bone-headed decisions I made, but that's a different issue.)
I've been pretty happy with my boxes and vendors. Support has mostly been good, and I've been able to drive the machines in when something needed fixing or I wanted to upgrade something. When I call tech support at PCs for Everyone, for example, I get a knowledgeable human within seconds. I don't tend to open the box (although I did some modem card swaps on the older, now-gone boxes), nor do any OS whacking such as registry editing.
But it's reassuring to know that, thanks to the choices in hardware I was able to make by going to a white box shop, I could do such messing around because I've got a case that's easy to open, the part sizes are all standard, and I wouldn't void the warranty by putting in somebody else's components. (Although, in all honesty, I'd most likely take it in and let trained professionals do the work, especially for the computer with which I earned my living.)
Is a white box (which may actually be multicolored, transparent, wood, or some other wild case mod), and a white box vendor for you? It depends on what you're looking for, your comfort level with the pros and cons, whether a white box vendor you feel good about is located near you, and other factors.
Here's some advice on selecting and buying from a white box vendor, based on my own experiences plus watching/kibitzing/helping over the years as friends and family got their own white boxes.