The processor might be a little light on the new MacBook as [MENTION=31330]J-see[/MENTION] pointed out. You might be better off with an Air. I find that LR and PS work well on mine (mid 2012 13" i7 512 SSD). The max memory is 8GB so I am careful to ensure I have minimal other apps running. I use
Memory Monitor to make sure I've freed up as much as possible if I'm going to be running more than LR (e.g. exporting to PS, NIK, Photomatix).
I use the Macbook Air while traveling to import in Lightroom (while making a second copy on a portable drive), I am consistently
merging to a single primary catalog on the Mac Mini and taking advantage of Lightroom's Smart Previews to keep select "mini" catalogs on the Air. Even with that approach, I am seriously considering upgrading the SSD to 1Tb using the
OWC Aura.
One thing to consider is to buy a refurbished model from Apple. I've done that for my last two laptops and the Mini. Adding AppleCare to a refurb is generally cheaper than buying new and results in an extended warranty. YMMV