Not every place will have a network connection, so if you want to make absolutely sure that you can connect everywhere you go, you may want to pick up a modem as well. You can get an old Psion travel modem for very cheap on eBay, etc., and it's an IR modem so it's short range, line of sight wireless. 99% of the places you'll go will have a phone jack, whereas about 1/2 of that (or less) is going to have network connection. Phone line connections are also a lot cheaper than network connections, too.
I've used an IR modem with both a T|X and a T|C, and the difference between Wi-Fi and a 56k modem connection is not very noticeable when browsing simple websites or checking email. I also have the Palm Modem (Palm Universal Connector sled) for my T|C, but I like the Psion IR modem better.
