Seriously netbooks with Intel Atom processors eg. N270, N280 and the new N450 have more than adequate performance for the usual office suites (including Powerpoint), email and general internet surfing. There is another Atom Z series processors (eg. Z510/520/530/540 etc), which is more power saving but expensive. You probably don't need those in a 10" netbook because many newer model N series netbooks can provide 5+ hour of battery life.
The only downside is the integrated Intel graphic chip used with these Atom processors, which is not good enough for High Definition video particularly internet flash video. The main reason is they are designed for low power consumption (longer battery life) at the expense of performance. I live in the Stone Ages and all these HD stuff doesn't interest me. Plus, why would I want to see HD youtube or vimeo on a tiny 10" or smaller screen of a netbook anyway??
The best bang for the buck now is the Atom N450 netbooks (bargains if you can find clearance N280 netbooks). Asus and Acer are the frontrunners of netbooks, but the three giants (Dell, HP and Lenovo) are also getting into the market. 10 inch screen is very good for general use and they are cheaper than 12"+ screen models. The smaller 7 and 8.9 inch screen models are disappearing (or being rendered into "tablet UMPC" (ultramobile PC) or "MID" (mobile internet device)), cuz most people find the screen too small for full screen webpage surfing (eg. at 1024 x 600 resolution, everything is too small to read unless you boost the fonts and screen DPI, but that distorts some of the displayed items).
One important thing - you can get the best performance on such a netbook with Windows XP and at least 1 GB of RAM (2GB is plenty). It is difficult to add RAM to most netbooks, but some if not many allows up to 2GB RAM if you know how to take it apart to replace it. I dunno about Win7 but at least many people find the older model netbooks struggle with Vista and 1GB of RAM.