Currently there are a few known issues with the phone.
1.) On some older models, GPS suffers the same interference the N97 did due to an improperly shielded antenna. This causes random drops in satellite connection and overall poor performance that seems to degrade even more as time goes on. Some users reported the GPS becomes completely inoperable after a few weeks to a month of time. Nokia has a fix for this and all new units (if you don't get old stock) should be free of the fault... or Nokia care can fix it for you if you stumble onto a handset with it.
2.) The camera lens is self mutilating and has not been confirmed as being fixed. The lens cover on the N86 sits too close to the plastic lens and if any dirt or dust gets between the cover and the lens deep scratches can be gouged onto the lens itself. These would not show up on any pictures, as they are too close to really cause any distortion, but they have an effect of causing light floods into the lens that show up as lens flares. Some of the floods are so profound they wash the entire photo. They've since redesigned the lens cover as shown below:
Initial:
New:
As you can see the lens now is squared off and supposedly raised similar to the fix they made for the N97. Nokia's official stance on this is the fix was to help with the lens flares and light flooding from the flash. They have not stated anything about this helping solve lens scratches caused by the lens cover.
3.) The slider itself can cause scratches to both the numeric pad and the back of the phone. These are completely cosmetic and may or may not bother you. The numeric pad is a simple swap if the keys get damaged and it bothers you... The housing itself probably not as easy, but again, they'd only be seen from behind with the slider open. I kind of see these as minor due to the mechanics of a dual slider phone.
Now that we've gotten the known problems out of the way, I'll say this about the device. It's basically a non-touch, S60v3 version of the N97. It is pretty decent, but the hardware spec is a bit behind the recent releases from most of the industry. The phone runs on an ARM 11 CPU @ 434MHz. It has 128MB of RAM, which is pretty sufficient for S60v3 (and abysmal for S60v5, and why the N97 really suffered), a glorious 2.6inch OLED screen, 8GB of mass memory, though you'll only find about 50Mb on the C: drive which can cause some trouble later on if you install items there (Why Nokia dropped C: down so low after the E71 I don't know, but they've started rectifying it now on the E72 and the N97 Mini that were just release, bumping both up to 250Mb of memory for C
. Although you technically should only be storing stuff like emails and etc on C:, some programs force installation on the C: drive (such as Quick Office) and other things like mms/sms can be set to default to mass media, but a lot of times that setting gets reverted. Don't ask me why. Regardless, my current i8910 only has about 25Mb left on C: after a clean install of the OS and I've been running fine... I just have to be careful and make sure everything goes to Mass Media. I'll bring up the i8910 later
The camera is pretty good. Again, there can be problems with lens flares, and if your lens self-mutilates, that's another story, but if you get a good one then all should be pretty golden. The low light photos are pretty astounding due to the larger lens. With the lack of a dedicated graphics chip, though, you're locked into old fashioned VGA video recording at 30FPS. Not horrible, but nothing to write home about either. The camera software was recently updated with some nice goodies like face detection and etc, but all and all it's not going to be as good as a feature standalone camera.
Audio quality is astounding. Just like all the recent Nokia device, the audio quality through headphones is nearing the best in the industry. The N97 and N86 suffer from a bit higher than average TMD (distortion) levels, but nothing that really ruins the experience. The internal speakers are a bit shrill, and lack any bass at all... but if you've never had a Nokia 5800 or other XpressMusic phone, you probably wouldn't notice. Build quality is said to be good, but... Nokia is hit or miss. If you get one that is shaky or poorly assembled, send it back and swap it for another. I usually have at least one small quirk with every Nokia I buy... it's getting the least annoying quirk that is the challenge. They're the best in the business when it comes to putting together a whole package, but they absolutely suck at quality control and early-software releases. I think the N86 has had a lot of its firmware bugs worked out by now, though, so that shouldn't be an issue.
Anyway, Samsung I8910 is basically your best competition right now for the N86. You should check it out. I picked one up in July and have had a pretty love/hate relationship with the device... but it's mostly love, and mostly hate for touch-screen only phones. If you can handle the glass as the only input method, the i8910 may just be the right fit. Everything is better than the N86, better CPU (dual 600MHz with graphic acceleration), better screen with double the screen resolution, 8MP camera with 720P HD video recording (at 24FPS, though the firmware is still struggling to do that perfect), and just about everything else you can imagine. It's bigger, though... thinner, but bigger overall due to its 3.7inch OLED screen. Build quality is amazing, however, and with no lens cover it won't self mutilate
Funny thing is, I'm almost in the N86 boat as I'd love to at least have the T9 keyboard and etc.
Finally, here's a nice nine page review of the N86:
http://www.gsmarena.com/nokia_n86_8mp-review-366.php
and if you have any specific questions, you can ask away or just voyeur over at the N86 board at Nokia Users:
http://www.nokiausers.net/forum/nokia-n86/
