My experience is with a larger age gap than most of our multi-childed friends have; we have 8.5 years between my son (currently 10 and a quarter) and my daughter (currently 1 and three-quarters). Most of our friends have 2 or 3 year age gaps.
Comparing my experience with theirs, the main thing I notice is that we all have our difficult periods at different times and for different reasons. For some specific examples:
they often have to deal with two in nappies at once, or an older one potty training while they have a newborn, whereas my son was fully independent (and indeed able to be a real help) by the time my daughter was born
I was plunged back into the world of sleepless nights and nappies and sore nipples after a good long gap, during which I had regained my equilibrium as a person, not just as a parent; whereas they get it all over with in one go (it's like the difference between making two small adjustments versus one large one, in some ways)
it's sometimes easier for them to find outings or activities that will interest both or all of their children at the same time, whereas we end up doing quite a few things with one child per parent so we can go separate ways as appropriate
they often find their children competing for their attention in the same way at the same time, whereas I can multi-task mine quite well (for example doing a puzzle on the floor with my daughter while answering my son's questions about his maths homework)
These are just a few examples but you get the gist. There are pros and cons each way and while I like my big age gap (the biggest problem has been people assuming that my daughter was a "mistake"!) it may not suit someone else.