New and updated features
Ethereal can now merge multiple files (you don't have to resort to mergecap on the command line).
A preview pane has been added to the file dialog.
The capture progress dialog can now be disabled.
The about dialog has received further improvements.
The behavior of Ethereal's dialog windows has been normalized somewhat.
The Windows installer can now associate standard file extensions with Ethereal.
Ethereal can be configured not to bug you about unsaved captures.
Ethereal can open help documentation using the default web browser.

New protocol support
DNP, ENRP, giFT, H.235, PacketCable, SigComp, SIR (Serial Infrared)

Updated protocol support
AIM, ASAP, ASN.1 BER, ARP, ATM, DHCP, CFPI, CLNP, DCERPC (DCERPC, LSA, NT, SAMR, SRVSVC, WKSSVC), EAP, ENIP, Frame Relay, GRE, H.225, H.245, H.450, HTTP, IAX2, IEEE 802.11, ISAKMP, iSNS, ISUP, JFIF, Kerberos, LMP, M3UA, MGCP, MPLS, MTP3, NCP, NetFlow, NFS, OSPF, PIM, RADIUS, RIP, RSVP, RTCP, RTP, RTSP, SCSI, SDP, SIP, SMB, SMTP, SNMP, SOCKS, SSL, T.35, TCP, VRRP, WBXML (User-Agent Profile), WSP, X11

New and updated capture file support
Radcom