Although the most sensible solution long-term, it does cause issues with the current exchange rate. Even the cheapest items will be quoted in hundreds of thousands of XBT, and the exchange rate itself doesn't look quite so appealing when it's 0.000129$/XBT.
I don't see why people can't just use the units that are most appropriate to the denomination. Use 150mBTC rather than 0.15BTC; use 20MBTC rather than 20000000BTC; use 24XBT (or 24uBTC) rather than 0.000024BTC. Is it so hard?
A dollar is 7,700 XBT at the moment. The dust limit is 54 XBT. Therefore XBT covers quite well the micropayment range and the commas make it easier to read then 0.0077 - 0.000054 BTC. Reading mBTC out of XBT is also easy 7,700 XBT = 7.7 mBTC.
For higher sums 123,456,789 XBT is 123.456789 BTC also easy.
I think people generally more used to deal with big numbers than with small fractions.
According to the thread an XBT (shouldn't it be XBC?) is a millibitcoin, not a microbitcoin.