So I've never used a gas oven until we moved house. I've got the instructions that came when it was installed and I'm doing as it says for which shelf to use. And following recipe directions for which gas mark to use. But everything seems to take forever to cook! It just doesn't seem to get very hot? Also if I try to put a full baking tray to roast vegetables for example it seems to really struggle to cook a full tray. It performs better with just a few measly pieces spread out e.g. 6 sausages and nothing else 
I can't really cope not being able to cook full trays.. electric oven could handle 2 full shelves of food e.g. roast chicken with roast veg tray above it.
I've read a few old threads on gas vs electric and quite a few posters loved their gas ovens.. What is your secret?