Not great, not terrible.

Released Devices

Only eight Windows RT devices were released. First generation devices originally shipped with Windows RT 8 and were later offered an upgrade to RT 8.1 and second generation devices shipped with Windows RT 8.1 as standard.
Production of all Windows RT devices had ceased by February 2015.
First Generation
Second Generation
ASUS VivoTab RT (Mars)
Microsoft Surface 2 (Covington)
Dell XPS 10
Nokia Lumia 2520 (Sirius)
Lenovo IdeaPad Yoga 11 (Venus)
Microsoft Surface RT (Georgetown)
NEC LaVie Y *
Samsung Ativ Tab
* Believed to be a rebadged Lenovo IdeaPad Yoga 11

Cancelled Devices

A number of other devices were planned that were cancelled prior to launch likely due to the poor reception of the Windows RT operating system.
Microsoft Surface Mini (Iris)
Nokia Lumia RX-107 (Vega)
Nokia Lumia 2020/RX-115 (Illusionist)