Update: As written by Matt and Xavier (below) - RFC 4408 was obsoleted by RFC 7208, that says:
SPF records MUST be published as a DNS TXT (type 16) Resource Record (RR)
Regarding the original question: The SPF TXT record is sufficient.
Post from Dec. 20,2012:
The SPF (type 99) dns resource record will be the successor of the SPF-TXT entry. According to this use both. Use SPF-RR with v=spf3 the SPF-TXT with v=spf1.
It is RECOMMENDED that a backward compatible TXT RR starting with v=spf1 be maintained
and
New software SHOULD look up TXT RRs if it finds no SPF RR, and MAY accept v=spf1 for backward compatibility.
and
Admins MUST NOT create RRs of type TXT that start with v=spf3.