Some of my friends already tested the lens against the FA*300/4.5, here are some first impressions:
1. FA*300 is quite a bit smaller and lighter (FA*300: 73x160mm, 935g, 67mm filter size. DA*300: 83x184mm, 1070g, 77mm filter size)
2. The FA*300 has slightly faster AF speed (Strange, isn't it? But it is true. My FA*2870/2.8 has faster AF speed over the DA*1650/2.8 too)
3. FA*300 has more pleasing bokeh (personal preference)
4. DA*300 isn't sharp enough wide open (inline w/
digitalcamera review), stop down to 4.5, both are about the same.
5. FA*300 produces more saturated colors while DA*300's colors are abit cooler (as w/ most FA lenses vs DA lenses)
The things they like about the DA*300:
1. Black finishing
2. SDM is very quiet (but not a big deal, especially we'd use this lens outdoor anyway)
3. Weather sealed (not actually tested)
4. Tripod colar
I wish Shriro would pass me a copy of DA*300/4 so I'd do a comparison myself ;p