Just visited Jordan including going to Petra for the 4rd time, no matter how many times I go it never gets old its amazing..for non jordanians be prepared to shell out some money 40jd for non arabs, 15jd for arabs from other countries, 1jd if your jordanian..worth the money, piece of advice walk it dont bother with the horse n buggy through the siq better photo ops walking as well, on the way back after totally beat sunburnt and over heated then take one of the horses if you are too exhausted to walk. :)
For those with sensitivity in lungs or get sick a lot WEAR A MASK I got sick all 3 times from the dust..fun time 6 weeks with broncitis after but small price to pay for going :D
Wear really comfy and good quality walking shoes!! Dont go for fashion be comfy

