1) reiserfs is a perfectly good filesystem. It is, I believe, the oldest Linux journaled filesystem (someone please correct me if this is wrong) so is very stable. Some people also claim that it is much faster than the ext3 filesystem, but this sort of thing is of course hard for an end user to actually test. I've used both ext3 and reiserfs for a Gentoo installation, starting from scratch each time with the same partitions, but I didn't notice any significant difference in the time it took to compile up to kde. So you pays your money and takes your pick basically.
One difference is that an ext3 partition can be mounted as an ext2 partition if you want to (though you obviously lose the benefit of the journalling).
2) It's safest if you stick to the versions mentioned in the LFS handbook while you are doing the initial install, as more recent versions may have different dependencies, possibly requiring packages which are not addressed in the handbook. The handbook actually recommends this in the introduction, and I quote :
This chapter includes a list of packages that need to be downloaded for building a basic Linux system. The listed version numbers correspond to versions of the software that are known to work, and this book is based on their use. We highly recommend not using newer versions because the build commands for one version may not work with a newer version. The newest package versions may also have problems that work-arounds have not been developed for yet.
Once you have finished the initial install you can always upgrade if you want to.