Yes. L2TP is quite secure. You'd have to read up on it for details.
(Reprinted from Windows Network Magazine)
"L2TP, which is new with Win2K, overcomes PPTP's security limitations by enlisting IP Security (IPSec) to encrypt data for transmission. L2TP wraps a PPP packet with an L2TP header and UDP header, making it safe to transmit the packet over the Internet. IPSec encapsulation then encrypts the packet and provides an unencrypted IP header that provides the necessary addressing information between the VPN client and VPN server. L2TP and IPSec provide better security than PPTP"
