To be fair, they're hit or miss. Due to circumstances I've used three extensively. The asus t100 and chi t300, which were both excellent in their price segment, and the lenovo miix 310, which was terrible (but that mostly seems to be due to w10 which took a vehement dislike to the 32 gb emmc storage).
I've also used ipads extensively and can say that windows devices are not ipad replacements or vice versa. An ipad can't do what a windows tablet can, but the reverse is equally true. Windows doesn't have the rich touch-friendly app ecosystem of iOS. I use both types of devices for the things they're good at, but neither can replace the other.
Even as a pretty big Windows fan, and someone who would personally choose a surface pro over an iPad, I find it impossible to recommend Windows tablets to people considering an iPad. The apps and user experience just isn't there when it comes to doing the sort of things people do on an iPad.
The cheapest iPad is less than half the price of the cheapest surface, and if you only need the iPad features then the surface is really expensive.
edit: Seems you can still get the old Surface 3, which only costs a bit more than an iPad.