After waiting for a long time, I have decided not to get the Samsung Galaxy Tab, for various reasons (most important being the price), this comparison might help you in deciding. For me it is simply the price, if I am to pay $600, I might as well get a full blown WiFi iPad and not worry about contracts.
Galaxy Tab does not have a WiFi only version as of now and carriers are bundling data plans with it, with the lowest starting at $15 for 250MB on AT&T (just like the iPad plans), to $25 for 200MB on T-Mobile. Looks like the Verizon's $20-plan, which gives 1GB, the best plan.
You can compare Samsung Galaxy Tab Prices at PCWORLD