Not dark at all. Not hoppy at all.... "hefe" means yeast, "weizen" ("vite'-zen") means wheat, or white, whatever. It's made with anywhere from 45% and up (typically 60-65%) of wheat in the grain bill. Specific yeasts are available for it. It's cloudy (or "white") because of the wheat and the yeast in suspension; it's great for homebrew because the yeast goes into the glass along with the beer. It's an ale, not a lager, not that that means anything other than it would be simpler to brew because it's an ale. It's on the very light-colored side of the scale. SRM's (color scale) will generally average around 8-10 or so (very light, but remember it will have a hazy/cloudy appearance in the glass), IBU's are generally in the neighborhood of 17-20, give or take a few points either side -- obviouslt not very bitter. Now, that's not to say that there isn't a good hops flavor, just pretty far down the bitterness scale; in fact, not a lot of beers are that low, few if any go lower.
This is NOT to say that the "wheat beer" put out by the BMC crowd is the same thing. Depending on the yeast used, and the fermenting temperatures, it can and does have varying degrees of fruity esters, and flavors/hints of clove and/or banana; again, depends a lot on yeast and fermentation temps. It's light and crisp but not thin; quite the contrary, it has terrific mouthfeel and is full flavored. Hops are just "there" and taste great, really a perfect fit when using traditional German/noble hops varieties. Flavor is delicious, but not "strong." You'll never forget it. It's become my favorite, and I am not overly fond of dark beer in general, either. I also like good brown ales; they're "dark," if you will, but NOT strong or overly hoppy; they've got a good malty sweetness to them, and if you brew your own, you can tone down the hops even more but most brown's aren't too heavy on the hops to begin with. A decent example is a Newcastle Brown Ale. I bring this up only to point out that not all "dark" beers have a "dark side."
I'm trying to think of a good commercial hefe, but I've never had one. That is NOT to say that they aren't out there, just that in my area, I've never found a good one so I can't recommend one for you to taste. Conversely, brewing my own, I've never had a bad one. Not even a "so-so" one. I love 'em. The closest thing I've had to one that approached mediocrity (again these are my opinions and are to be taken as such) was a True Brew kit with Munton's wheat LME and it was darker and, well, sort of syrupy and the head retention was not great (some hefe's will produce massive foam when poured! Don't worry, though, it's delicious and will float a bottle cap until the head dissipates). Before that, I had used True Brew Bavarian Hefeweizen kits (mainly because I got started with extract - still do a lot of brews that way - and also I received a lot of gifts that were kits) and never once had a problem, but all of those others had Coopers LME and they were all VERY good brews. What MIGHT have happened, and this is not an accusation, is that the LHBS (no longer in business) switched the fresher (by date stamp) Coopers that probably had been in the kit with Muntons that probably was on the shelf and getting old or well past its expiration date. And it was old, by a long time; I checked only after bottling day when I noticed things were a little different but it was too late to do anything about it by then.
Anyways, even that one was still far far better than any commercial offerings I've been able to find.
LONG post, sorry - go to the Commercial Review forum and check out the Wheat Beer section. That might help you find one to try before you take the plunge.
- Tim
This is one of the most informative and helpful websites around, plenty of assistance for beer to be found here! (rhyme intended, DOH!) 
