We use the Lightspeed system and it is working across multi stores and just integrating with Magento stores currently.
Its a great system to use, but like all POS systems has advantages/disadvantages.
Just use there demo and you will soon know.
Another avenue I am looking at for another company is Cloud based, which so far I am leaning towards VEND + this will help with a future move to XERO accounts as well :)
Any questions you might have about Lightspeed I will try and answer :)