The kernel configurations for Debian Lenny on Debian's latest official kernel configurations, with some key modifications by myself. These changes center around architecture-specific optimizations, and pruning out some stuff that doesn't apply in that context. For example, Intel-specific options don't make sense for an AMD Athlon kernel and vise-versa. The timing settings were also changed from the default 250Hz to 1000Hz, and the schedulers set to be aggressively desktop-friendly. This will incur a very slight amount of overhead in the raw amount of potential CPU horsepower, but the payoff is a huge boost in responsiveness when multitasking or placing the system under a heavy CPU workload. This is especially noticeable in games, multimedia, and heavy multitasking environments, so I feel it's well justified for a non-server environment. So fundamentally, the largest differences between the official configs and my own are the CPU-specific optimizations and the scheduler settings. Each respective kernel was also compiled with the highest known-safe CPU optimizations relative to each architecture.
See Also: CPU Architectures