We had one fitted last week. We are so happy with it.
The fitter (who was private, not IKEA's own), was initially not thrilled when we asked him to fit an Ikea kitchen, but at the end I think he was secretly impressed.
The delivery was fine, everything we had ordered was present. We had to send some worktops back (as our old walls are too wonky and we needed wider ones) but that cost £10 to return when they delivered some wardrobes to us.
For refunds etc we've had to go back into the store which is a pain as it's over an hour's drive away, and some of the kitchen staff were not that knowledgeable about customer service type stuff but overall it's been fine and we'd do it again.
Planning - we did it ourselves using their software online. I took weeks to do this to get it perfect and it allowed me to really think where I was going to put things even down to the best place for tea and coffee. Everything flows really well for us and everything has a place, with lots of extra storage. I'm glad I did it this way.
The internal fittings are brill and really useful for storage.
We shopped around and feel that I've got more value for money with our Ikea kitchen compared to other stockists.
If I were you, I'd do a plan online and then chat to a private fitter to get a quote and see what they think- they can see if your walls are straight, whether you'd need to move any pipework, measure up and make sure it'll fit ok etc.
Good Luck - I love ours, it's totally transformed our house. x