Fixed income ETFs make little sense to me. The point of having FI in a portfolio is to generate a regular cash stream and smooth out volatility through diversification. Throwing an FI ETF into the mix may actually raise portfolio volatility because hedge funds and day traders will be tempted to time FOMC moves. Also, if you're a covered call writer (like me), the option chains are so thin on FI ETFs as to be useless. In this market a buy-write strategy can easily see you position called away. No thanks to fixed income ETFs!
I'll have more to say on ETFs as time goes by. I am conquering the world wide web of finance, one pithy post at a time. ;-)