Just switched back myself. The main reason being the lack of after sales support, Apple's just doesn't compare to Dell's. Price was also a factor, take a look at this Dell system I ordered for my sister, I challenge anyone to find a comparable Apple machine for the price.
480.86 (including delivery and V.A.T.)
PROCESSOR AMD® Athlon 64 X2 Dual Core Processor 4400+
OPERATING SYSTEM Genuine Windows Vista Business - English
HARDWARE SUPPORT Collect & Return, 1 Year Service
MONITOR Dell 19" Silver Wide Flat Panel (E198WFP)
MEMORY 2048MB 667MHz Dual Channel DDR2 SDRAM [2x1024]
HARD DRIVE 250GB (7200rpm) Serial ATA Hard Drive with 8MB DataBurst cache
GRAPHICS CARD 256MB ATI® Radeon® X1300 Pro PCI Express graphics card edit
OPTICAL DRIVE 16 X DVD +/- RW Drive edit
KEYBOARD Dell Entry Quietkey USB Keyboard - UK/Irish (QWERTY)
SOUND SOFTWARE Integrated 7.1 Channel High Definition Audio
SPEAKERS No Speakers
FLOPPY/MEDIA DRIVES 13-in-1 Media Card Reader
MODEMS No Modem
MICROSOFT SOFTWARE Microsoft® Works 8.0 - English edit
Also included with your system
Gedis Bundle Reference List D07C12a Dimension C521
Dell System Media Kit Dimension Resource DVD for Vista (Diagnostics & Drivers)
Shipping Documents C521 English Documentation with UK Power Cord
Order Information Dimension Order - Ireland
Standard Warranty Collect & Return, 1 Year Service only