I'm using a 15.4 inch screen laptop, it's not as much about the screen size as it is the graphics card and screen display.
Quote:
PROCESSOR AMD Athlon™ 64 X2 Dual-Core processor TK-53 (512KB/1.7GHz)
Genuine Windows Vista® Home Premium Edition
DISPLAY High Resolution, glossy widescreen 15.4 inch display (1680x1050)
ATI RADEON® Xpress1270 HyperMemory™
MEMORY 2GB Shared Dual Channel DDR2 at 667MHz
80GB SATA Hard Drive (5400RPM) edit
CD writer / DVD player (Combo Drive)
Dell Wireless 1390 802.11g Mini-Card
WARRANTY AND SERVICE 2Yr In-Home Service, Parts + Labor, 24x7 Phone Support
All this for $1,121. Dell Inspiron 1521, you can add another $375 worth of components if needed, and that resolution should be perfect for 4-tabling.