Make sure you read a conversion guide or two. John Beardsworth's guide is good. Read Adobe's disclaimer which tells you what will work and what will not work post migration. Suggest you understand how to use Lightroom before you move, especially DAM capabilities. Make sure you prep your library in Aperture before you begin, Lightroom doesn't offer as many capabilities, make sure you capture what data you need in Aperture first. Then there are several issues with the conversion process. Check my prior responses, which should help.