I guess part of the massivity comes from Studio 6 being built on Visual Studio 2010 andsupporting both AVR and ARM, but who knows. I have it installed and it works OK with JTAGICE3, the newer and cheaper version of JTAGICE. That box in turn ONLY works in Studio 6 so be careful if you consider it.
So far i only use Studio 5 for production code because of another quirk of 6: it does not fully support C++ debugging! Go figure. Class member variables never show in the debugger and Atmel has acknowledged this so Studio 5 / JTAGICE 2 it is for C++ so far.
And let me agree with DiligentMinds; once your code goes over a some not so big limit, you _will_ need a debugger to iron out the wrinkles. Luckily there is the built in simulator that lets you debug algorithms and software constructs, but that won't let you interface with the real world from code executing in the target at full speed.
Now the Farnell price for JTAGICE 2 is a joke. As they say, caveat emptor. You can find the same thing at significantly more reasonable prices elsewhere. That said the box will set you back a couple hundred euros in any case. Now you may ask yourself, what is the difference between a programmer and ICE. Actually, the only similarity in this case is, well, the case. They look the same and both do programming. But only the ICE 2 does debugging. Its name says JTAG but in addition to that it does PDI, debugWire, aWire, SPI, in fact all debug protocols supported by any Atmel chip. Other than that it is a Nexus compliant device supporting 6 simultaneous program counter breakpoints and 2 data breakpoints. Some of those in ranges, some as watchpoints. I could go on but since Atmel does not pay me for advertising their products, you can check the rest from their documentation.
Debugging is an integral part of any software creation workflow and if you don't have a debugger, how you gonna do that?
I have experience with this. My company owns an AVR JTAGICE-MKII, and it is a great ISP/ICE pod. BUT-- Atmel's latest greatest software IDE (that is based on Microsoft's IDE) will never work with it. I got this straight from the engineer at Atmel writing the code that supports ISP/ICE pods. "It's a matter of policy." (He said). The new IDE is incredible steaming pile of "bloatware" though, so we just stay with the latest 4.xx version (plus the free GCC compiler add-on), and all is well.
That is not entirely accurate. In fact it is the other way around (they say - i never tried). Studio 5 does not support the JTAGICE 3 whereas Studio 6 has no problems with JTAGICE 2. I know the last part for a fact since as i write this i have in front of me a functional combination of Studio 6, STK600 with UC3C1512 processor and JTAGICE 2 connected to the JTAG input of the STK. The debugger has no problems reporting target voltage and processor signature. The latter is a sure sign that communication works normally.
P.S. the fact that the tools are massive in disk size and that they take their time loading never bothered me. Disk is cheap and if you spend hours, days and weeks writing code, who cares about the few tens of seconds the IDE takes to warm up. I know i don't.