While talking with Mark [1] today he mentioned having a problem with Linux on a client's machine. It seems that the latest kernel, 2.4.1, doesn't like the client's hardware—it doesn't boot at all.
Now this client has an AMI MegaRAID controller, in addition to dual processors. The reason for the upgrade, other than the occasional kernel panic, is to have better network throughput, as the networking stack in 4.2 will actually work correctly in an SMP configuration.
Only it doesn't work. Mark was able to track down the problem to a call to reqeust_region() which seems to possibly have undergone a return value change since 2.2 and this particular driver wasn't updated; there's no contact or authorship for the driver other than Dell Corporation.
But the general consensus of both Mark and I is that Linux is slowly sinking into software bloat and general chaos. There are design decisions that Linus Torvalds is making that hamper the growth of Linux (one of the bigs ones—no revision control system. Another—he hates modular kernels (and modular in this sense doesn't mean kernel modules, more a sensible ABI or API between the kernel and various drivers and subsystems. Oh, and no enterprise support in the Linus' version of the kernel). A kernel split is, I think, imminent.