I have been battling with this debate for some time now.
I currently have a mid-2011 iMac and no laptop. I have been waiting... waiting and waiting for something to buy that I really really liked.
I've bought since then a Surface Pro 2, Lenovo Yoga 2, rMBP mid-2014 and tried them all out, but returned them all for various reasons. I actually liked each of them, but probably in the order of rMBP, Lenovo then Surface (the Surface 3 is much better than 2 however).
Last night I was very close to buying the rMBP 2015 (with 256GB), but they were sold out at my local Best Buy, so I was going to opt for the 2014 15", but changed my mind before purchasing.
I am still debating on the new 2015 13" or the 2014 15", but I am wondering if I can wait till June/July to possibly get a new 15" if they come out then.
I currently have at my disposal a 10% mover's coupon, $85 in Best Buy rewards and $50 for an education discount, so there is some flexibility to move around.
Too many decisions...