I was on Liberty last October and I agree with you on past experiences on other ships about the hard sell. It does put you off as nobody likes to feel pressured or awkward, the whole point is you've paid for a nice treatment you want to enjoy it. I avoided facial's this time (as they try and sell you loads of stuff) and went for hot stone massage which was amazing. There isn't much they can try and sell you from a massage apart from the oil. I also did a learning massage class with my husband. It was $60 or something and you got the massage oil to take away. We really enjoyed it and it was very interesting.
I wouldn't personally bother with the hair salon, as I have been disappointed by both of my experiences.
Book early though, as soon as you get on board. First day specials and sea days tend to have better deals.
I personally thought the spa was nicer on the Voyager of the Seas as it had a big jacuzzi downstairs in the gym area and they also had a couples Rasul treatment suite (self applied mud treatment, incase you don't know) which is lots of fun! They have replaced this with a teeth whitening clinic on Liberty, which all 4 of us had done, and was quite expensive, don't think it worked that well and the follow up products you need to buy are expensive.
What is the point to the boxing ring (which replaced the jacuzzi)? I didn't see anyone using it at all when we went to the gym, and it seems to take up a lot of space.
Have a great cruise, Liberty is a great ship. We are off on Independence on the 27th August.
I hope my spa experience comments are of some use to you.
Got our cruise docs yesterday, can't wait!