I got a code for the "starter" version of the game from a friend, which lets you play up until the first major boss. While playing it, I discovered another side of the DRM. Not only does the game require you to be online, but all events are actually handled server-side (movement, attacks, enemy placement and actions, etc.). This means that if your internet connection has high latency or doesn't have a lot of bandwidth and gets bogged down easily by data transfer, you'll experience lag in the single-player mode of Diablo 3. That's one of the main reasons I won't be buying the game.
Main: i5 2500K@4.6GHz w/Zalman CNPS10X Performa, Intel DZ68BC, 8GB G.Skill DDR3-1600, PNY GTX 470 + EVGA GTX 470, ASUS Xonar DX, ADATA S510 120GB, Samsung 1TB F3+1TB F1+2TB F4, Kingwin LZG 1kW, Lian-Li PC-9F, Dell U2212HM+S2209W, Win7 Professional.
Laptop: Dell Vostro 3450, i5 2410M, 8GB DDR3-1333, AMD Radeon HD 6630M 1GB, Intel X25-M 80GB, Seagate Momentus 750GB, Win7 Home Premium.