I'm always cautious of reporting 'localiser established' during the intercepting turn because if the intercepting angle is great enough the roll out may exceed half scale deflection; usually attributed to lazy vectors from ATC or you've flown a shoddy procedure. In either case if there is potential for intercepting greater than HSD, you're not established on the localiser. Realistically however, if the turn will capture and remain within the tolerance and you are certain of remaining with the tolerance, there is no reason not to make the call.
That said it's far better to allow yourself an extra second or two to roll out, check the needle, and report established or make a correcting turn. At this stage of the approach the workload isn't that high to require an early radio transmission anyhow.
Edit: Many replies added whilst entering my 2p here!
Last edited by GeeWhizz; 20th Dec 2011 at 09:50.