A dedicated GPU can't be called a "small difference", not for quite a few people that is. Personally, I don't care much about how it could be used as a ( graphics ) tablet, but the faster CPU and GPU compared to what Apple currently offers in their 13 lineup could be very important to many people ( assuming they found a way to also properly cool the thing ). At the moment, this is all just guessing... we don't know which exact i5 / i7 CPU models they've put into the Surface Book or which exact Nvidia GPU is used. It might easily be just a load of marketing bull, so just wait until the first models are shipped... then we'll know more.
In the end, I think the morale of the story is that Apple has gotten lazy over the past years. Sure, they've made some stuff thinner, added some fancy color options and after a crapload of waiting, they finally offered an ultra-portable notebook that has a nice screen ( the ports cutting, etc. is debatable... it most likely does not affect many of the users who were in the market for such a device in the first place ), but have they really brought anything *new* to the table in the past N years? I don't really think so... they've admittedly improved on existing ideas, they are undoubtedly masters at repackaging and reselling ideas / technologies for huge profits.
...at least currently, Microsoft seems to resemble *the good old Apple* more than Apple does itself. They seem to be trying to put more effort into actually coming with new ( *innovative* ) ideas to the table... only time will tell if these ideas lead to success or not, but they are at least trying and I'm quite sure that there will be plenty of people giving some of their newer products a shot ( myself included ).