I've been majorly impressed with shareprice.co.uk. The live prices are meant to be contended on a first-in-first-out basis, but I have never, ever been disconnected in many weeks of using it. I have a monitor on my desk that just shows my share portolio, live, all day long. That is both bad and good. Bad, in that you can't help but look at it every 10-15 seconds; I must check it a thousand or more times per day. Good, in that this regular checking allowed me to see the Rockhopper craziness almost the moment it started happening, profit from it myself, and get some of the people here, who may otherwise not have seen it, in on it.
The phone app is as good as the website. Again, I have never been disconnected (other than losing signal). It updates rapidly, can display your portfolio details, display charts, manage alerts - a very decent product somehow for free, and with no advertisements.
Interestingly, shareprice.co.uk is run by Interactive Investor. I get a feeling that we might find that it comes at a price in the not-too-distant future!