My 3-year old Acer Desktop (running Windows Vista, Windows 7, Ubuntu Linux and Arch Linux) died in the end of 2011 and I decided to try Mac OS X instead as my main home desktop. The cheapest option from Apple is Mac Mini 2011 and I chose to buy the cheapest option at S$788 ( http://www.apple.com/sg/macmini/ ).
The spec is fine for me, Intel Core i5 2.3GHz, 2GB DDR3 RAM, 500GB 5400rpm HDD, built-in Intel HD3000 graphics, 802.11n WiFi, Bluetooth, Gigabit Ethernet, Thunderbolt, Firewire 800, USB 2.0, HDMI, SDXC Card Slot. I use it with a 20 inch Compaq monitor (resolution 1600 x 900), an Acer keyboard and a Logitech wireless USB mouse. The 4 USB ports are not enough for me so I use a USB hub as well. A cheap web camera is also attached. I also use a 1TB external USB HDD (Western Digital Mybook Essential) as the backup disk using Time Machine.
The weakest link is the 2GB DDR3 RAM which I intend to upgrade soon. Mac OS X Lion is 64bit and it seems to require more ram than Windows 7 x64. USB 3.0 would be nice but we may have to wait for next-generation Intel chipset with USB 3.0 built-in.
I have no problems with the Mac Mini so far after 3 months of use other than than the occasional slow response which I hope to fix after upgrading the RAM.
Under Windows and Linux, I usually use Firefox as the main Internet browser with Chrome as the backup. But with this Mac Mini, I tend to use Safari more often.
I have no problem to build applications (e.g.: libusb, libftdi, OpenOCD, pyusb, etc) with Mac Homebrew since I am familiar with the terminal environment under Linux and Windows (Cygwin/MSys).
MPlayerX and VLC are the two main video player for me. iTune is also used occasionally.
I have Microsoft Office for Mac 2011 installed but I am not using it very often.
The App Store for Mac is quite convenient, however not many apps are available for Mac OS X compared to iOS ( I have an iPad 2).
Edit: upgraded to 8GB RAM (4GB x 2) and now it funs much more smooth. I also installed VirtualBox and then quite a few VMs (Windows and Linux) and they work fine. Good thing is that USB seems to work fine as well under VirtualBox.