[Symbiote]

It doesn't have a function key row, which is annoying when you just want to press F5 10 times, or Ctrl+Shift+F10. It also doesn't have separate arrow keys etc.

Being able to join it together isn't very useful -- if you can type on a split keyboard, why would you want to join it together?

But, it's a decent option that you can simply buy. Many of the better options are sold as DIY kits, or at least require editing a text file and re-flashing the keyboard to change the layout.

There are reviews of some other keyboards here: http://xahlee.info/kbd/ergonomic_keyboards_index.html (and the DIY options under 'DIY').