Cact,
wat's the bonus worth? 10k? 20k? whatever it is, it will be made back easily... let's put it this way, 5yrs from now when u're making 10k/mth... it's only 1-2mths pay. it seems alot now becos we're paid on a lower scale now... so if the opportunity is there and it's wat u want - grab it.
just fyi, i know someone who gave up a 72k bonus when he left his previous company. he was offered a 6-fig sum to stay, but he still left. he never looked back and he is much much happier now...