Strictly speaking no IDE is needed for Squeak/Smalltalk either but, as with most other languages, programming is much more enjoyable with one. It was partially a search for a decent Python/Ruby IDE and a persistent environment that led me to find Squeak. Also I think Squeak is best described as a "computing environment" and differs from what many will think of as an "IDE". Another example of such an environment is Oberon.

PS: Squeak can be used headless. Look up Seaside for one exampe (including smalltalk web development via the browser).

In case you didn't know: You can install a squeak vm via easyDebian. A new v4 virtual machine is available in the testing repository. Then I just grabbed the v4 platform independent files (image, sources and changes) and the thing started without complaints.

I have not yet done any serious programming and I didn't check sound and network.

Performance is okay, a bit sluggish but usable. The extra buttons of a three-button mouse can be emulated with Alt or Ctrl. The v4 GUI looks a lot more polished than the v3 did.