We use AIMS and it works fine. As mentioned above every day of the year has points allocated to it. What points you use this year determines your 'seniority' next year - lowest points gets ranked highest. So if you bid for only 1-pointers, you're guaranteed to get everything you ask for next year. If you do the same again you'll stay on top every year; if you bid for Xmas, Easter, summer holidays etc you'll get them all - but you'll probably be at the bottom of the seniority list next year. If you play the system you can have everything you want every other year, or everything you want from a more limited selection every year. Or somewhere in between. Once the bidding is complete and leave is allocated you can then see what's available and live-bid for anything remaining with instant approval. They have a calendar and every day has a number reflecting how many leave spaces there are. Right now I could take the whole of July if I wanted to. I think it works very well.