I am going thru a trying time with my mum passing away a few weeks ago...and have been off track and want to get back on track...I am planning to purchase a fitbit either tonight or saturday and wondering if anyone else uses the fitbit with success? Did you use it for a week or so before deciding on a calorie range and go with the normal EM2WL figures until then?

So sorry to hear about your loss, and unneeded stress on life, which I'm sure will be continuing for awhile.

If your normal daily activity and exercise consists of walking, then it can be decently accurate for TDEE. Slow jogging it starts to lose it, faster and other activities it will underestimate your calorie burn.
That's why their website makes it so nice and easy to replace a time period with say HRM burn calories or other calcs.

But, you can still use the data from non-exercise days to nail that activity level burn better. So many discover that despite a desk job, they are actually Lightly Active according to MFP or more, not the sedentary they had used, on non-exercise days.

I used a BodyMediaFit, same theory.

Only thing to be aware of, those devices all base their calorie burn on your BMR. They calculate it with least accurate Harris formula.
MFP uses newer Mifflin formula.
Both are based on studies of people at healthy weight already, so the BMR is inflated when overweight. That means reported calorie burn will be inflated.

And if you got your bodyfat% estimated and use most accurate Katch BMR calc, you'd have to tweak your FitBit height so it was using the correct value, if there was much difference to correct anyway.

What's nice is, after using it for a couple weeks to confirm your figures, don't need to wear it again until routine changes in some major way. But then again, it can be motivating seeing your steps and stairs live.

Yes, I use my fitbit to help determine TDEE. Mine was significantly higher than the Scooby calculations, so I had to adjust for that once I figured it out. I love mine!

I love my fitbit and I love that now that it's set up and syncing with MFP and I've got my TDEE calculating right, it gives me adjustment calories when I work out enough that i need to bump up my calorie intake. I haven't been doing NROL, just walking, which makes it one less thing I have to log. But when I do other activities, it's easy to enter it too. I enter it in Fitbit then let Fitbit send an adjustment to MFP. I've found this was more accurate for me than logging it into MFP.

I love that I can go to the Fitbit site, enter a range of dates under weekly tracking and see my calories burned vs calories eaten in graph form. Makes it really easy to see I'm eating about 200 calories less than my TDEE.

I use my fitbit to work out TDEE and an HRM for my non-walking/running work outs. I used it for about a month before calculating my average TDEE and used that. Until then I used it week by week to get a rough idea, tied in with Scooby calculations which were reasonably close for me anyway.