My moggies have been eating Iams for 10yrs or more, and thrive on it. It's a complete diet in itself, so you don't need to feed them 'wet' cat food as well -- although mine do appreciate a bit of variety and the odd sachet of something juicy, too.
You don't need to feed cats very much Iams -- portion sizes are quite small -- and it's easy to over-feed, so you have to be a bit careful that you don't end up with fat cats!
Iams pellets are ideal for cats who live indoors and use litter trays; there's less to clean up and it's much less smelly/offensive.
You MUST ensure that your cats have plenty of water available, however.
It's also worth bearing in mind that some of the more specialised varieties cna get quite expensive. Always check the 'price per kilo'. Bigger bags are generally cheaper BUT my cats do get bored with eating one flavour for a long time. So you may need to get a couple of properly airtight tins so you can buy big bags at low prices, and swap between varieties to keep cats happy. And you definitely need airtight tins: the bags are resealable but the seal isn't perfect, and it seems that some of the flavour escapes over time, which again makes the food less interesting for the felines.
Another thing I have noticed is that when I've tried the cats on own-brand supermarket dried foods, after eating Iams, they have been far less keen. Sometimes it's a struggle to get the cats to eat other brands... so be aware that they may get very familiar with Iams, and then not want to eat much else!