anyone use timesheets?

Sonar keeps a record of the time a project is open, under Project> Info > file stats ther is a field called editing time. This is what the help file says about it.
Editing time
The total time you’ve had the project open, from the time it was created to the last time it was saved. This does not include time spent editing the project since you last saved it. If you want to update this value, save the project.

Hofa has a free plugin for timekeeping:
 
http://hofa-plugins.de/plugins/4u/

I still prefer a slightly old fashioned approach.  I have designed a time sheet in the form of a table and printed out a bunch of them.  I keep one for each client.
 
Software timekeeping many not include hours that are still being done on a job in other areas. It might account for the time using Sonar but not the hour before or after doing something else. Watch that.
 
I have a stopwatch nearby and start it as they pull up. Then after I have finished totally working (and that may include another hour doing special edits and backup etc) I stop it.  I stop it to go away and have a break and take calls etc. I restart it again as I start work.  It shows accumulated time.  I round up to nearest hours too if over 1/2 hour point.
 
The best time to fill the timesheet in is right after the finish for that day. I detail day and date and hours and rate etc. Also I have an area to write down what I did. This has been invaluable in costing future jobs that are similar. eg produce a whole album for a client. (It gets into hundreds of hours!) Hopefully I am charging for all these accounted for hours on a given project, mostly I am.  When there are a lot of hours involved negotiation may take place as to a better rate but it is nice to have exact figures on how many hours you did do and what was done in them.  You will then have a much clearer idea for how low an hourly rate you are willing to go for a given number of hours completed.
 
I don't always time myself doing things like composing original music for pleasure etc.. But even that is worth noting down because that information too might help you later estimate a paid job that involves a lot of composition.
 
How you manage hours and break them up into the various parts of a big production like an album is another whole topic.  I have done enough now to see patterns where things worked out very well and more quickly too.  And also where many hours are lost in very small gains etc..
 
After 35 years of being in the business I am still keeping timesheets. You think I would know by now! It still amazes me how often a very unusual job comes along though that you have never done before or kept a time sheet for it.