Oh God, it was amazing. I was in a fair bit of pain when I got to hospital (3 days latent labour before waters broke - some contractions were full on and lasted minutes, so I got almost no sleep, but they just never got regular) but as soon as I got into the water and relaxed, the pain went. It was a miracle. I could still feel the clenching up when I contracted, but it was painless. After an hour or so it started to really hurt again, so I took gas and air and that more or less killed it till the end. I abused the g & a - breathed it constantly - but even crowning didn't hurt much. I was so stoned that I have no idea if I did a poo or not, but DH says no. (Waters broke when I was doing a big one at home, so maybe I was, um, cleared out, so to speak). Frankly though al I wanted was everyone to sit down, shut up and let me concentrate on labouring, which they did. I never even needed an internal exam, and it was my first birth.
They had a change of shift and the new mw was alarmed by how hot the water was and tried to get me out - I absolutely refused, and they just poured lots of cold in instead for the pushing stage. I gave birth leaning forwards, up against the bath. I remember this absolute certainty that the weight of my body would cause such pain if I got out, but in water it was fine. It was honestly never unbearably painful at any stage at all, and I am a wimp with pain - I take painkillers for leg waxes.
Hospitals often have much nicer pools than home ones. Mine was like a bath made for a giant - I could float, be completely submerged, and lean up against the back in total comfort. The bath at home didn't even cover my belly by the end of pregnancy, and didn't help labour pains, and an inflatable wouldn't have been as comfy to lean on.
I'd take a bag of ready-made ice or two along from a shop (not home-made, as industrially frozen lasts longer) in an Eskie, and get your birthing partner to hand you some in a cup between contractions, to cool you, if a hotter bath helps the pain. (I was spitting the ice out as contractions hit so I could suck on the g & a again, then just holding a hand out as soon as it ended, eyes closed, for more ice - my DH has never offered such attentive service!) Baths can get too hot and uncomfy for me after a while, ice kept me comfortable, and maintained my body temp. at a good level while also hydrating me. I'd have had to get out otherwise, I think, the mw told me a lot of women do.
My only anxiety about a second birth is if both pools are in use. A pool, and I know I can do it.