Kernel differences / Switching

Hiya. I'm still running Debian Sarge on the latest 2.4 kernel, and I notice mentionings on the forum here of how it's recommended to always update to 2.6, especially if one were going to dist-upgrade to Etch. I'm probably not going to go for the upgade just yet, but I still have some questions about the kernels in the meantime.

First of all, what big differences are there in 2.4 and 2.6 that I would notice or possibly be able to take advantage of? I know that in terms of a physical machine, 2.6 seems to support hardware better and some various other newer Linux "technologies" (udev, etc), though I'm not sure how that'd translate to particularly useful on a virtual machine like with Linode (especially when I already have the system installed using 2.4-era technology). I've also heard that 2.6 is a little slower in general.

Second, if I decided to switch, would it simply be a matter of changing that option in the Linode boot configuration, and then theoretically everything would still be fine, just running under a different kernel? Well, Firehol might need the proper .config, but other than that, do you suppose it would be seemless? Most of my installed apps are straight from APT, but I've done some custom things in C, and also compiled my own versions of Hybrid IRCD and Hybserv, for example. Recompiling things isn't that big of an issue, but I'd want to be prepared for what the task of kernel switching might entail.

Anyhoo, thanks in advance!