I should try this lens at the same time with the Tamron 70-300 USD on my Sony a58. I just ordered both (since I was unetschlossen) and various own tests subjected clearly not under laboratory conditions but very extensively and practice. When choosing lenses, the image quality is crucial for me always and deliver both lenses my feeling absolutely equal, and done properly. Tamron is theoretically brighter but in practice I have not noticed. Also autofocus is in both the same speed. What has ultimately led me to SAL is to keep:
1. Weight and size (Tamron is significantly heavier and larger. If you are traveling and with the lenses in your backpack makes excursions, every gram is a burden and a lot of space you have in your backpack anyway mostly not)
2. processing (it seems to me to be clear of the SAL-quality)
3. Sony lens (div. In-camera image-correction intervene)
4. Price (SAL 40-50 cheaper than Tamron)
5. Handling / Operation (SAL is handy, with Tamron is the GeLi if the other way is placed, difficult)
Conclusion: A great lens! Together with A58 an ideal tool for telephoto and macro shooting (the latter related)