I had several week long trials of proquote (one for each family member) some time back, mainly for UK level 2 data.
Overall I thought it was the best available, but the charts were poor and I would not have traded off them and it was very expensive.
I went on to subscribe to www.moneyam.com level 2 data. This was less than half the price (around £67)and was uncontended. Moneyam was also better than advfn in my opinion.
I grew to like the moneyam service as its possible to customise the appearance of the level 2 screen with different colour/bands etc. and the actual order book data with moneyam enabled more rows of orders to be visible within the level 2 window - without having to scroll down the page.
jTrader - you should try MoneyAM through QuoteTracker. Takes their data to a whole new level, particularly if you want high end charting: http://www.quotetracker.com