I've had one since last summer.
What do you think about the TF700 transformer pad of Asus? Its a solid tablet, well built, excellent screen. Expandable storage, solid build quality.
The OS is Android. Started with 4.0.3, upgraded to 4.1.1, then 4.2.1. Each time, Asus has improved and smoothed the rough edges while keeping a very stock look and feel.
Is it a good tablet? Yes
Very reliable? Mine has been.
Is it a good choice? Unless you get it for 300-350 with a case or other accessories, I'd have to say no. Its nearing the end of its life span and will be EOL'd soon by Asus. The internal NAND has slow write speeds, which causes stuttering whenever you do a task that writes more than a few MBs to the internal storage. Its improved significantly with the 4.2.1 OTA though, but still noticeable. Under 4.1.1, you hit the Update All button in the Play Store for several apps at once, the TF700 became unusable until it was done. Under 4.2.1, it slows down, but you can still use the device. If you copy a few GBs of video from your desktop to the tablet, consider it unusable until its done. I'd also criticize the mono, rear facing speaker. It produces very weak sound.
Is it better than Windows 8 tablet? Almost every Android tablet from a tier 1 vendor is better than a Windows 8 device.
For a 10in tablet right now, I'd look at the Nexus 10 or the Sony Xperia Z if you need expandable storage.
For a 7in tablet, the Nexus 7 still reigns supreme. Kinda disappointing that it didn't get a refresh at I/O though, its Tegra 3 isn't going to sustain it through the year.