Nothing magical about the Cisco flash cards, we have never bought them unless it was required part of the configuration and then it was always the smallest we had to purchase. Cisco does not make them, they purchase them and then slap their sticker on them and then mark them up 1000% to 2000%. Only specific brands of the older PCMCIA type flash cards on 7200's and sup
2's, but we have never had any issues with any CF cards for Sup720's, 2800 and 3800's. One of the tricks we used do on the PCMCIA cards was to peel off the Cisco sticker to reveal the manufacturers branded sticker and then buy those.
Internal flash SIMMS are very specific. When upgrading these we only purchase the ones that the manufacturer specifically says they work on the model of router they are going into. We almost always use Kingston, PNY, or Crucial for those.
Why would you care about Smartnet on a CF card that costs $20, verses Cisco's price of over $500 with discount. For the savings you can purchase