A comment on another thread got me interested in this unit.  I want to use it for recording multi tracks live and possibly for 
studio work.  A couple questions
1. I know I need an ipad or tablet to control this.  Can I record on the device I am controlling it with?
2. Is the touch mixing decent to work with?  This question is more universal.  I have done a lot of mouse mixing but never any touch screen

The XR18 can record directly to an iPAD.
I'd go with an iPAD Pro to make sure you've got enough CPU to handle both.
You'll probably want an iPAD Pro for the screen real-estate.  
 
Using a touch-screen interface works fine for mixing.
Most times, you're making adjustments to a single channel.
 
We use an XR-18 for rehearsal.
Amazing what it offers for the money.

wow.  so it is possible to simultaneously record and mix with the Ipad ?  Yes the xr 18 is amazing for the $.  I have one on order
 

If your mix is "set and forget", you can actually close the mix app (just open it when adjustments are needed).
If you're going to record and mix simultaneously, I wouldn't get too crazy with the realtime mix adjustments.  
The iPAD Pro CPU is decent for what it is... but it's not near desktop performance.

Been looking at this, a venue I play weekly uses this for their house, and the sound in this particular listening room is awesome. Wondering, however, if it might be worth the extra $$$ for a Presonus StudioLive mixer/control surface. It records also to SD card, has full mixing board functions using the UC surface control, and motorized faders, control surface functions. A lot more $$$, but could double in my studio as well as for live recording. Any opinions on this?

I am considering the Microsoft surface go  vs the ipad.  It runs windows, has more connectivity

I just ordered the Microsoft surface go.  $349 (slashed $50 for black Friday week sale) It has much better connectivity than the iPad, has 64gb storage vs the 32gb for the base priced iPad, and runs windows.  I got tired of shopping deciding.  so I finally just said F it and made the call.   I will try to post updates on how I like it.  MY Behringer X air 18 arrives tomorrow.  

A side note to the Pianist.
There are actually a lot of mixer/recording to USB set ups these days. I went through a long process of comparing features and channel count etc. Then you read reviews and log on to the user groups for the products. Each has it's ups and downs. The biggest complaint was always the device loosing connection during a show or just not working. I chickened out and bought a Soundcraft analog mixer  :) I have my Tascam us1641 and a Yamaha 01v if I feel I need 18 channels at once.
 
But in the end I think the  X32 would have to be the one I would get because I just have to have those faders...
That was a big drawback for me,,, I pay $800 for a box with no controls and another $800 for an iPad???

the prevailing wisdom seems to be that you are better off using an external router than you are using the built in wifi of the Behringer.   I shall see. 

If you're out and about yes, use a dedicated (external) router.  There's a lot of interference in clubs.
The onboard WiFi is just fine is you're at home/rehearsal.