The current version of the iPad OS - iOS 4.2 - supports Apple's proprietary AirPrint protocol and printers that support this protocol can be used to print directly from within apps that have printer functionality - such as Apple's 'Pages', 'Numbers', 'Keynote', 'Safari' etc (their MS Office-like suite) as well as many other apps.
Printers that are not AirPrint compatible can be used via a number of third-party printing apps - I have PrintCentral, for example, which enables you to print to almost any WiFi printer (AirPrint compatible or not) using the in-app AirPrint menu. Basically it's totally transparent to the user - PrintCentral very cleverly appears as a print option in the AirPrint menu and then 'converts' the AirPrint format to that supported by your WiFi printer.
If you don't have a wireless printer - say it's connected by Ethernet - then PrintCentral have a (free) app for your PC or Mac (assuming, at least, that your PC or Mac have WiFi, of course!) that routes the wireless printing from your iPad via the PC or Mac to your cabled printer.
The program has lots of other features too; the one I like the best is the ability to upload/download files and folders directly between your PC and iPad without needing to sync via iTunes or go via a cloud service - like Apple's MobileMe.
I've used PrintCentral for several weeks now and it's great. You need iOS 4.2 (the multi-tasking version of the iPad OS) but, if you're buying a new iPad it will almost certainly have that on. Also, PrintCentral needs to be running in the background (it could hardly work otherwise!).
There are several other third-party apps too and I'm sure other Forum members will give you their opinions.
Best advice though is don't buy an Android tablet...;-))
Tim
Scotland