I like my Fitbit Flex. Although I wish I had the new Fitbit Charge, which has a watch on it. You're supposed to wear it on your non-dominant wrist and it's not comfortable to also wear a watch.
This is the issue I have with my Flex as well. I have a watch that I like very much and I wear it all the time. You're right, it does not get along well with the Flex. The online web widget let's you specifiy that you're wearing it on your dominant hand though. However, I once had it celebrate 10,000 "steps" as a result of stirring spaghetti sauce rather than walking.
In general, I use the online web tools more than I really care about the steps the tracker is counting. I log a lot of activities the tracker doesn't really count properly (like if I'm on a stationary bike). I also used the software to log everything I ate in order to successfully track down a mild food intolerance.
As for the tracker itself, I get a lot of garbage results because I cycle to work. The problem isn't that I'm on the bike, but that vibrations
through the handle bars set off certain functions that are triggered by tapping. For example, to track your sleep manually, you can tap your Flex until you feel it vibrate right when you get to bed. When I'm cycling there is a particularly shoddy road that is bumpy and I get all kinds of vibrations from the Flex which thinks it's being tapped like crazy. Then it shows crazypants stuff in the sleep logs.
I blieve the "tapping" from the cycling is also what results in a lot of zero logs. I get lots of entries for: "0 steps, 0 duration, 0 cals".
I like my Flex just fine because I don't rely on it for anythig in detail. If I move on to something more advanced, it will probably be much more
advanced like a traithlon tool that I could use for distance bike rides and swimming. But that's going to be a long ways away from now.