I have a NeoAir and really like it; I prefer the short (48") model and put my empty pack under my lower legs. Having tried both the NeoAir and BA Insulated Air Core at colder temps (down to around 30), I found the the NeoAir could go about 10 degrees colder than the BA IAC before I'd start losing heat through it. I also found the crosswise baffles of the NeoAir are more comfortable (for me) than the lengthwise baffles of the IAC.

But, if you are comfortable on the IAC, I wouldn't be in any hurry to replace it if you have other changes that would produce better weight savings for the same expenditure. You would just need to be aware of the temperature limits, and add a closed-cell pad to the BA IAC below those limits.

If you do decide to go for the NeoAir, take a look at the "all-season" model - the R factor is about double the regular NeoAir (and the BA IAC), and I think it's still a few ounces lighter than the IAC. Then your decision between regular and all-season models comes down to the question: "how often will I be camping below 30 degrees?" If the answer is "only once or maybe twice a year" then I'd go with the regular and add a closed cell pad if needed.