The main issue with unsigning your zone is that DS records should be removed from parent zone well in advance before you unsign your zone - you should wait for those records to expire from caches before you remove your DNSKEYs and RRSIGs. If some cache for some reason keeps DS records, he will refuse to use your unsigned zone at all.
Additionally, if you (i.e. resolvers which query your zone) use DLV, your zone should be removed from DLV too. Today nobody supposed to use DLV. IMHO.
It is about the same in the "regular" DNS - when you want to change a nameservers, you remove old nameservers only after NS TTL to expires.
The biggest problem with DNSSEC is that people think that it's something extremely complex. IMHO.
DNSSEC is no more complicated than DNS and SSL, and everybody uses the two, not even knowing that they are complicated.