I have the 15" new 2011 standard MBP.
For me the screen size is just perfect for me. I tried running Traktor on my gf’s 13" but found myself staring at the screen longer to see whats going on. It looks ok on the 13" but IMO the 15" is just the right size. I’m very happy with it. 
That 15" with the upgraded screen looks perfect! I think I am pretty much sold on one of them.
I have a friend who brings his 21.5" iMac with him to every gig. He got a Pelican case that fits the iMac and he rigged his S4 flight case onto it and wheels it around everywhere. Not my idea of portability but he says he needs the large screen size. It is nice to have that much power in your machine but my 13" MBP is plenty for me!
I use a 10 inch screen with no problem, just 2 decks but with advanced mode, 4 decks is possible but dont need them and wouldnt use them, i have a big toggle knob for deck browser which works for me. Thinking of getting a 15 inch sony vaio soon though as ive seen a lovely one with hd screen, illuminous orange or green shell, backlit keyboard and i5 processor, think it might work a bit better then my intel atom processor
Hahaha wow! I’m not dissing that, it’s fucking hardcore. I wouldn’t do it, though.
Honestly, if your using 2 decks, its not that horrible
P.s. stiffy, i’d rather get a mac than a sony, and i’m a pc guy.
I’ve been wondering this recently:
Is it possible to show decks C & D with everything?
I would rather have the close up waveform than the full waveform.
It would also be nice to have an option to completely get rid of the tracklist/browser
why would I need to look at the tracks/playlists in the middle of a mix?
My software would handle 3 decks on that screen pretty easily I think. Still I don’t have a soundcard which could do it 
Cant justify the price for something with shitter specs, ill be getting an 8gb model, i7 after finding out they do them, the build is big chunky plastic thats durable, plus i cant see myself ever changin operating system. Ive heard good things about these and they look a lot nicer then the typical light up apple version which costs like a grand extra here in Ireland.
Thanks for a ll the replies. It’s sad that NI doesn’t allow us to fully hide the tracklist. With 2 decks it’s not bad, and also with 3 decks and a sample decks is fine. But 4 decks in advanced mode makes it it for a lot of standard screensizes impossible to show the effects. So effects toggle on/off as you expand/collapse the advanced functioanlity of decks 3/4. This sucks and I hope NI fixes it. We don’t need to view a couple of tracks while in the mix. I’d rather view all tracks or none.
I just upgraded from an old Black 13" MacBook (1280x800) to the brand new 13" MacBook Air (1440x900), and I love the new extra resolution. I personally don’t play with 4 decks at this time in Traktor, but I do plan on picking up an Akai LPD8 to use for sample deck usage. But I can already see that screen space won’t be an issue now with the new MBA. The screen resolution is actually why I held out from the i5 13" MBP to the release of the i5 13" MBA… well worth the wait.