The standard IDE leaves a lot to be desired. But, from a development point of view, they have made an enormously complex problem into a simple download-and-write-code answer. They have done some amazing things in getting that featureless IDE to work for virtually 100% of the users.
On the other hand: if I can't get Eclipse to work for my hobby projects, I will toss Arduino and rip it up AVR style for anything more than a one page project. I am a software engineer as a daily job. Coming home and writing code is what I do for fun. Being able to use the Arduino for super quick-and-dirty proof of concept circuits, and using various components is awesome.
Although, after I have discovered how to use the Wire library for external banks of EEPROM, or how beautifully simple it is to control a servo, or what have you. I am ready to start dropping some mad codeto to make my robot sing and dance. That's when I desire a real IDE.
Am I capable of using TextMate and commandline to develop? Sure, heck - sometimes I do it all day. All the projects that we do at work are all Eclipse external Makefile jobs, so I am 100% confident in doing it in a minimalist way. But Eclipse has a nice spot in my heart. I use it for Python, PHP, C/C++, ASM, Java - I would use it for email if it would let me (God knows I hate Entourage!). After using Eclipse all day, coming home using the home-brewed-looking IDE is a drag.
Bottom line, I would not own multiple Arduinos, if they didn't have such a turn-key IDE. But after you get your LED blinking, or your motor spinning, most of us are ready for a complex IDE with project exploration, code linking, folding and all the other time saving features that are in the main line IDEs.
I am super pumped to get the Eclipse Plug-in that Jantje has working. (I have a few OS X glitches to work out) It looks like most people on Windows that have tried it, have it working nicely. So for anyone looking for an alternative, give it a go. It looks promising.
Now that I have read this thread I am going to give the Xcode plug-in a whirl too.
Thanks,
Nick