First, let me start out and warn all the technogeeks that this isn't a technogeeky review. While I'm impressed with the knowledge of electronics, circuitry, LEDs, and reflector types that many users of this forum have, I don't have any skill or education in that direction myself, so if that's what you're looking for, you might as well stop reading here.
However, for those of you who appreciate a little insight into potential purchases and can deal with a more generalist viewpoint, then hopefully I can offer something of use.
One additional caveat: I only received this light today, and so can't give any insight into durability or any of the issues that arise from extended use.
So why bother with the review at all, you may be wondering? Well to be honest, had someone else done a review like this here before, I probably wouldn't have purchased this. I'm not saying don't buy it, only that it doesn't really satisfy what I was looking for.
Getting into the particulars then, let me start by saying that the simple packaging of the Cygolite Expilion 700 set the tone for disappointment. It's in a cheap plastic tray, like an assorted cookies gift box, and each component is in a translucent plastic bag. Everything was fine, just packaged in a basic, utilitarian way.
Handling the headlight and associated bits is just fine. The unit is appropriately weighty, and the accessories feel like solid plastic pieces. A closer look at the light reveals fairly simple casting for the head, one that shows little detailing or marks of attention. The handlebar clamp looks good, though, and I love the short locking screw which only takes a few turns to loosen and remove. Compared to the Niterider Lumina mount with it's very long screw, this is a blessing.
Tactile impressions are fine...until you reach the light switch. It's over sprung and vague to the touch, as it is to the ears as well. It makes a click, but it's virtually inaudible. Detents are imperceptible. It is lighted though, which is not indicated in the Cygolite website, so that was nice, but otherwise the switch sucks.
Clicking through the modes is straightforward, without much to note there aside from the fact the fade-to-black from Mid, High, and Boost to off is nice. None of the other light modes fade the light though. A push of a couple seconds switches between two menus; this is easy enough.
Inserting and removing the battery is a cinch, but the USB port cover is not. It's tiny, and getting it reinstalled securely takes attention. On a couple of occasions I thought I'd secured it, only to find it popped open later. I've read a couple of stories about the cover tearing, but think a little basic care in removal and installation should allow plenty of life
Mounting the light on the included helmet mount or handlebar mount is easy enough, though removing it is a pain, requiring quite a bit of strength. Maybe over time this will loosen up.
On the mounts, as I said earlier, the handlebar one has it's charms derived from the quick release, but two things nag. First is narrow range of off-center adjustment horizontally. Probably not a big deal, as the 3 or 4 degrees available is enough to reach across a lane, but still, it feels abbreviated, and it's probably exacerbated by the second thing, which is the absence of detents. It just silently turns left and right in this narrow range, and is susceptible to being knocked out of position by accident. I'd definitely prefer a clicking or ratcheting type of action here.
The quality of the light itself is pretty good; it's on the warmer end of the cool scale, with just a touch of yellow. The beam is broad and totally circular, with a nice, solid, bright core that fades out to the edges. No annoying artifacts are present at the edge; smooth all the way out. I'd like to see some shaping to the beam, because it offers a fair amount of throw, but is hard to judge how much glare is getting into the eyes of other road users.
I used the light side-by-side with a new NiteRider Lumina 500, and have three comments on my perception of the comparison: 1. the brightness levels of the 700 and 500 seem about the same. We didn't do any proper distance measurements, and while I think the E700 had a slight advantage, it was less meaningful than I was expecting with nearly half again as many lumens as the L500, and 2. that the L500 has a cooler white temperature. This is, of course, a matter of preference, but I like the cooler, more technical light of the NR. Finally, 3. the NR seems to have a little more "beam control," particularly at the top, which is defined somewhat, whereas the E700 is not.
In sum, I think the Cygolite Expilion 700 lacks some refinement in most areas, and while I like the various light modes in practice as much as I'd anticipated, the main interface points-- the switch and the USB-- are it's weakest, and really have me wondering if the interchangeable battery and flash modes are worth it. I really like the form factor of the Serfas True 500, which also has the interchangeable battery and a much better switch, and I love the build and finish quality of the Niterider Luminas; maybe the L650 would perform just as well or better despite a lower lumen rating? One thing for sure, if the Cygolite delivered better, I wouldn't be asking these questions, because it had a lot going for it, including output, a full kit (helmet mount, wall charger, USB cable) and a great price.