I am 25 week pregnant with my 2nd, due in May. My daughter will be 5 in July. We never planned for them to be this far apart. However, like you, I was surprised when it took us 2 1/2 years to have a successful pregnancy (1 ectopic after 2 yrs. trying). our first was no problem.
Anyway, i don't have experience yet, with this age gap, but I am very excited about it, and have been reminded that God knows what he is doing! I am excited that while my oldest is in Kindergarten every morning, I can do things with the baby and have one on one time. Often I see moms with little ones so close together and they all get dragged around to each others things. the baby just kind of tags along. Also, I now realize this is the best thing for my husband and my personalities. We both love order, structure, and are strict about house rules, cleanliness, etc. I think having little ones close together would have been very hard. I don't want to be the mom that becomes so lax with everything by the 2nd/3rd kid because it's just too much. We would like to parent our 2nd the same way we did our first and have the same expectations and boundaries.
I also babysit 1x per week for a 20 month old whose sister is the same gap that mine will be. Her mom loves it. She said it's great having big sister be so independent and helpful. I am already cautioning myself to not expect my older girl to be "too" helpful! It will be tempting to have her be a runner for me!
Since getting pregnant, I have had lots of people, old and young, tell me that they had a 4 or more year gap between siblings and that they were and are close!
ps. here are a few tips i have for getting pregnant. of course, I am not a dr.! i am convinced that i needed to be at the lower weight i was when i first got pregnant and that the 10 lbs. i was carrying helped in preventing me from getting pregnant again somehow. so, try to get yourself to the weight you were when you first got pregnant...if you've held on to some baby weight, try to get rid of it. during your fertile time, take mucinex or robitussen or something with guafenisen in it. it helps thin all the mucus in your body :) and i've also heard that vitamin B6 and B12 help.