1) as the tiles are flexible and only a few mm thick your subfloor needs to be perfectly flat and smooth. and imperfections will stick out like a sore thumb and may affect adhesion, causing the edges of the tiles to peel back.
2) it's a messy business if you use the old tar-like adhesive they always used to use to lay vinyl. not sure if you still need to use that stuff though, F44 or F45 acrylic adhesive might do it. check mfr's recommendations.
3) they are a nightmare to remove when the time comes to change them.