-Work/life balance: yes, flex hours exist, but there is so much to do (and as far as I can tell, a lack of manpower to do it) that you will be often staying late. It is not uncommon to see more than a handful of people staying past 7pm, and very often I see a decent amount of people still at the office at 6pm. Of course, no one is forcing you to stay, but deadlines need to be met.
-Coding style: varies from team to team. There is no company-wide standard, which is frustrating; everyone (okay, at the minimum every team) does something different, and there is a LOT of legacy code.
-Culture: mix of a lot of inherited Nortel employees sprinkled with new grads. Unfortunately you won't be finding a silicon valley type environment here, there are not many young hires (they exist, but we are numbered). The upside is this means your team will likely be able to support you easily, but at the cost of a culture hit.
-Technologies: generally speaking, very out of date. This is expected as Ciena acquired a part of Nortel; however, the tools (in my opinion) are REALLY starting to show its age. There is a transition process to move to newer tools, but it seems to be taking an extremely long time. IT tech also feels lackluster - there are recent plans to eventually let employees pick their laptops on refresh (starting this year), but that remains to be seen. Mobile computing options can be difficult since the dev environment is Linux, but the current laptops run Windows.
-Nicheness: if you're looking to be a SDE generalist like many SV jobs, then I would give this a second thought. You will learn a lot about embedded development and develop a great sense of low-level stuff, but my opinion is that these are niche skills - career progression is a concern if you do not want to stay with embedded development forever. A lot of work at Ciena is interfacing with hardware and making hardware work reliably; paradigms like OOP/Functional programming/etc. are not practiced (unless you're on a team doing much higher level design).
-Pay (and to some extent, responsibility) transparency: the lack thereof, really. Not many are comfortable talking about it, and as far as I can tell there is no way to find out the pay (or even pay range) that comes with promotions. Promotions seem to be based on experience, but there's no HARD criteria (to my knowledge) on the skills that need to be met for this to happen. Almost anyone at the company for more than 2 years will be either SDE 2 or SDE 3, unless you proceed to management. The determination of seniority (before you hit the management ladder) seems to be very subjective.