It's often recommended because they're awesome, especially for the money. And if you've followed closely, they've been one of (if not the most) the most reliable LGA 1155 motherboard manufacturers, plus they've had amazing prices. The color scheme for their Gen3 boards is the best IMO, too.
Got my board for $150 and will definitely buy ASRock yet again if they keep producing such top notch boards. For that much I got 3x PCIe 2.0 (x8/x8/4x or 16x/0x/4x), and it'll work at 3.0 speeds with Ivy Bridge. It has front panel USB 3.0, a CLR CMOS button on the back panel, a debug LED, power and reset buttons on the motherboard, eSATA, front and back panel FireWire, 7.1 channel audio, optical and coaxial, 4x SATA 6Gbps (2 off Intel chipset, 2 off Marvell controller), 6x USB 2.0 plus 2x USB 3.0 on the back panel and many other things. It also has an 8+2 power phase design if you're overclocking. In short, it's hands down the best Intel board you're gonna get for $150, and as of now stability has been solid.
Only thing I'd like to see change is the UEFI interface, which looks just a bit dated. It is very well organized and all the features you need are there, however. I'd give the board 4.5/5 stars.
Another worthy mention is the Z68 Extreme3 Gen3. It costs $122, and the only things you lose in comparison to mine are the third PCIe slot, 2x SATA 6Gbps, the debug LED and power/reset buttons, the FireWire, and the optical and coaxial. You do get video outputs like DVI and HDMI and support for Lucid Virtu and ISRT, but for enthusiasts IMO the IGP is largely worthless and you won't use ISRT if you have a decent-capacity SSD. Great bang-for-buck overall, too.