This is a fine product and really very small. I used it to connect to a ATmega168 and a ethernet network of course.
There is one very important issue with this product, I've found this remark on the internet:
"the TPIN+/- polartiy is indeed incorrect on this module. TPIN+ must connect (by way of the transformer) to pin 3 on the RJ-45 jack and TPIN- must connect to pin 6. The TX+/- path has wrong polarity as well (TPOUT+ should go to RJ-45 pin 1 and TPOUT- should go to RJ-45 pin 2). However, wrong TX+/- polarity is less likely to cause a problem due to the prevalence of the auto-polarity feature in most 3rd party PHYs. None-the-less, you must fix the RX+/- polarity issue and should also fix the TX+/- polarity and RBIAS issues."
I'v made a special cable to change the tx/rx polarity, and then the module worked fine.