I don't want to lie - I've found it very hard. But my DS is younger than your DD. He was just over two when DD was born in March. He's now 2 3/4 and she's nearly 6 months. He's lovely with her but I've struggled with:
A very screamy baby when the toddler needs me and wanting to give my toddler the emotional things he needs while holding a wriggling or screaming baby who is trying her best to get my attention. Or a baby who will not be put down and yells if I do, but the toddler is also resisting something like teeth brushing that sometimes requires a more robust approach.
No sitting around in cafes or watching boxsets while establishing BFing this time around - a quick feed perched on a bench in the cold and tense, waiting to leap up, throw the baby in the buggy and run after toddler.
Going through toddler tantrums and hitting or pushing phases, while out with newborn who has just done a poonami or is cluster feeding or whatever. It's all just so much more hard work.
Having very disturbed nights with the baby, and then facing a long day with a super energetic toddler.
Just the overall physicality of having a toddler and their needs - all the up and down of getting drinks or snacks and playing with them and colouring in and the endless, endless requests - while having the velcro baby attached to you.
So I don't know - that list seems very negative but I just wanted to be realistic. It's bloody hard work. I am exhausted all the time. And my PFB was sooooooo easy. So super chilled out. And my DD just. Is. Not. She is NOT happy with anyone but me and will work herself into such a state if I am not holding her. I am really taken aback by the difference in them.
But, they are lovely. I could not do without them and it's spectacular seeing another child of mine who is so like my DS but then so different and so wonderful. And these are the hard years...or so i tell myself. And your DD will be nearly four and that is SO different to a nearly three year old. It's hard but it's worth it, basically!