Guy, thanks for the suggestions.

Resizable window: a no-brainer; noted.

Comments: already there in 2.5, and we've resumed preview uploads (please check the daily builds and the list of new features). In short, /*comment*/ in formulas.

Tab indent in formulas: I don't think an customisable option will benefit anyone but the most advanced users (such as yourself). I favour changing the default setting; 4 sounds about right, don't you think?

Select/case: the CHOOSE function goes part-way, and in fact you can cobble together an alternative to nested-if using CHOOSE, but it's not hugely intuitive. I'm guessing you want:
SELECT(field, value1, result1, value2, result2, value3, result3, defaultResult)?
Equating to: (pseudocode)
IF field=value1 THEN result1 ELSE IF field=value2 THEN result2 ELSE IF field=value3 THEN result3 ELSE defaultResult
This would only work for exact matches, so you couldn't say "if A is between 3 and 6".

Or how about:
IFELSE(condition1, result1, elseCondition2, result2, elseCondition3, result3, defaultResult)?
Equating to: (pseudocode)
IF condition1 THEN result1 ELSE IF condition2 THEN result2 ELSE IF condition 3 THEN result 3 ELSE defaultResult
This would be more powerful than SELECT, but for those which SELECT would work for, IFELSE would be more verbose.

Perhaps we need multiple new functions to address these kinds of problems.
It would help if you could have a look at a few of your deeply nested IF statements and checked to see what would be most useful - give examples.

Guy, your suggestions have been taken on board.

Tonight's build of 2.5 will include:
* Resizable formula editor window
* Tab stops of 3 spaces (found to be ideal)
* IF function extended to support IF(test1, value1, test2, value2, test3, value3..., else_value) - no more nested IFs