More than double the throughput and real server support, plus a much bigger increase in SSL termination capacity than the earlier upgrades in the lineup. The 540 is where the ADC line moves from "handles more" to "handles a fundamentally busier environment."

Eight 1 GbE ports instead of four give you more flexibility to separate traffic types, dedicate ports to specific server pools, or build in extra network redundancy, which matters more once you're managing 100 real servers instead of 35 or 50.

Yes, that's specifically what the jump in SSL processing power is built for. The 540 terminates thousands of encrypted connections per second, so applications that are mostly or entirely HTTPS won't bottleneck the way they might on the 340 or 440.

Yes. Content rules based on URL, domain, cookies, or headers, and Direct Server Return for high-bandwidth responses, work the same way across the entire ADC lineup. The 540 just has more capacity behind them.

Yes. The appliance, Energize Updates, and Instant Replacement or Premium Support are sold the same way across the whole ADC lineup, so pricing structure doesn't change as you move up in model.