I have an Acer ZA3 (0751) with 11.6" screen and the low power (as in it uses less power and also is less powerful) Z520 cpu. Screen res is 1366 x 768. It has an 8meg Intel GMA500 GPU, which steals main memory, but my netbook has 2g ram so it's not much of an issue.
It runs Photoshop fine but it can get bogged down a bit with large images. The screen width on my netbook is fine, but the height is sometimes not quite enough. It's seldom a problem. For photo editing I hook up an external mouse - it's just horrible to to do it with a touchpad.
I don't often fire up Photoshop, but instead I use a freebie Photoshopish type software called Paint.NET which isn't nearly so much of a resource hog as Photoshop:
http://www.getpaint.net/index.html
Paint.NET's interface is VERY much like Photoshop's, and it has pretty much all the same default tools, and there are a LOT of plugins available. If you are familiar with Photoshop, then you can start using Paint.NET immediately with pretty much no learning curve.
Highly Recommended.
If you like it - and I very much DO like it - toss 'em a few bucks since it's a freebie which is supported by donations. They ask for $12 but I tossed a $20 bill in the kitty last year and will do the same this year because I WANT this software to continue being developed and supported.
SIDE NOTE: I picked up a 9-cell 7200mAh battery for my netbook from Amazon for 50 bucks about a year ago and it gives me a solid 8+ hours of runtime with the built-in wifi. If I'm using my external high-power Alfa wifi card, 5-6 hours. The stock 3-cell battery claimed 4 hours of run time, but in normal use in low-power mode it usually runs around 2.5. At least...it used to. Lately it gets down to around 50% and then the netbook decides it's dead and hibernates. The netbook was purchased on Black Friday 2009 so the original battery didn't last much more than a year.
If I were buying a new netbook, I would absolutely choose a netbook for which an aftermarket "BigggAsss Battery" is available. It does just about double the netbook's weight, but to me it's totally worth it.