i had one done by gears that had done about 300 miles since they rebuilt it stripped 3rd gear the first time the car came on boost after i cruised it home to devon from mad.
id had it in the car for a year while i did work on it hence hardly any miles. i didnt expect them to warrent it for that amount of time and doubt they would take my word for it on the miles. not all bad though as it was 500 quid for the box and sold it broken for 300..
i went for the big tooth t5 after and it took a fair bit of use before i sold the car but wouldnt want the noise for regular use if i had the choice again..