Myself, I have a pure Slink installation, being a newbie. I'm currently running 2.2.10 kernel for plug&pray and sound. I also use 2.3.18 kernels on boot floppies for experimenting with USB with few problems. The only problem I've actually had with the 2.3.x kernels is my sound doesn't seem to work, but I'm sure I've overlooked something. As far as the differences between Debian 2.1 and the kernel versions, I'm no expert, but like I said, I've had no problems running 2.2.10 or 2.3.18 kernels with Debian 2.1. Right now I'm waiting for 2.2 to freeze before I upgrade. After that I'll probably try to use a 2.3.x kernel again.
This is just my personal experiences. YMMV. Cheers, John Gay