I've been a fan of VO for several years now, and without them my favorite bike wouldn't be anything like it is! I've purchased a lot of parts by other manufacturers from them, but I've also used some VO products quite a bit as well.
I equipped my Univega with the fillet brazed, chrome plates steel constructeur racks (which they no longer carry). This was before they pre-drilled their racks, so needless to say installation was...intense. But in the end it was well worth it, because they look great, are amazingly strong, and are custom fit to my particular bike. All I really need on this bike would be a small front rack like the Nitto, but since these fit perfectly they sit low, right on the fenders. I never liked the way the Nitto sits a good inch higher than it needs to on many bikes. I originally bought these over the stainless versions because they were cheaper, but I also like the smooth, plated fillets as opposed to welds. Not that I hate welds or anything, I just like these better.
My Long Haul Trucker utilizes several VO products, and I have no complaints about any of them. I bought a VO 1.125 threadless headset shortly after they began offering it. I can't remember if this was a Grand Cru model, but I want to say it wasn't because I don't remember it being very expensive. Regardless, in several years of commuting in every kind of weather imaginable, I would swear it was brand new if I didn't know better. The same could be said for the threadless VO stem. (Of course, how much could a stem really wear in that time?) The same bike also has a Grand Cru bottom bracket, which is still silky smooth and play-free, which I would hope would be the case with any modern bottom bracket.
I've also purchased the Belleville handlebars and a Model 1 saddle, but I haven't used them nearly enough yet to comment on them, other than to say I think they both look nice for the price. The saddle seems a tad crude in construction compared to a Brooks, and it seems like it will take far longer to break in, but I really do like the shape and the color and feel of the leather. Plus I got it on sale so it was a good $20 cheaper than even a B-17, let alone a Brooks Pro, which I'm assuming it is modeled after. I rode it only a few miles, and while it was rock hard, after a few minutes I no longer even noticed it. My brother had an early, unpolished set of VO fenders on his commuter. They were good and functioned well, but he later bought some Honjos and likes them better. Of course, they costs three times as much as those VOs, too.
As far as customer service, I can't really comment. I've never had any need to contact VO, and my parts have always shipped promptly, so I've been happy. One thing I would like to see from them though: A frame like their Rando frame, but with clearance for 42mm 650b tires, vertical dropouts, and those upper-mid fork eyelets for their Rando rack. I like their Rando frame, but it only comes in 700c and with far too little tire clearance, and I like the Polyvalent but it seems mostly designed to be a city bike with backward swept handlebars. Looking at the specs of the Poly, I'd have to get the 54cm frame to get the top tube length I want, and on that size the top tube would be a good two inches lower than my Univega, which would require me to raise the stem to odd-looking heights. The 57cm's top tube is considerably longer than I want, though, so that's out as well. I need a 55-56cm frame with a short top tube. So for now I can't consider either of their frames, although I really like them for the most part.