My experience with the H22N has been top notch, however there's a couple problems with certain media that needs a firmware update, which seems to take far too long.
For example Prodisc R05 burns at even 18x with the newest firmware on my Liteon 20A1H, and 16x on both my Benq 1650 and Samsung 182M. The H22N with it's latest firmware has absolutely no write strategy for this media (which has been around a while) and defaults to 4x. At least the newer H42N supports this media and burns at up to 16x.
Some lesser known media such as AML002 and UME01 burn very poorly on the H22N, which seems at least somewhat improved with the H42N.
These characteristics aside, I see no reason to avoid the H22N. But I believe the H42N to be superior, if not for it's greater media compatibility, but for it's faster 8x (and possibly other speeds), (which it does 6-8x Z-CLV instead of 4-8x Z-CLV).