Great stuff - interestingly, I'm going to be doing the same as you, i.e. ditching my iPad for a base rMBP, I've got a 2 year old MBA which is fine, but fast becoming the kids' homework machine. The screen does tire my eyes after a while so I'm hoping to reduce this a little with the retina. Otherwise a base i5 (albeit with 8gb RAM) flies for all the stuff I'd do on my iPad.
Only thing I've not put on there, but will do on the new one is LR (I've used the iPad to import photos for a first cull before importing onto my winPC for proper editing).
As an aside, found anything to spend the £60 gift card in the store
iTunes gift cards, as it was 2 years ago, are far more useful to me at least...