You still need to patch your kernel. But you have to know that a lot
of external modules still don't support some of the changes that
appeared in 2.6.19 (the death of config.h for instance). My advice if
you want an upgrade is to go for a 2.6.18 for at least a month or so
before switching to 2.6.19, or just keep your 2.6.16 if you have no
urgency in an upgrade at the moment.