DL,
No experience of trading equities, but I do use the orderbook for trading futures.
The one thing I will say is that Spreadbetting and using L2 are totally at odds with each other - if you continue to SB, then your trades should be lasting long enough not to worry about L2 data or the spread (which your SB firm will adjust to their favour anyway). L2 data is useful if you are involved in making the market that SB's derive their prices from - where DMA is absolutely necessary, with a fast connection to the exchange, dedicated from end, and so on.
I guess the same is true for equities markets, both used in different ways for different types of trader.