Google Sheets FILTER function to solve all IFS suggestions
Several aggregate functions have IFS variants (SUM, SUMIFS, MAX, MAXIFS, etc.). The IFS functions only exist due to poor design (strong coupling).
If we separate filtration from aggregation, we can use our normal aggregate functions on a filtered range. For example, PRODUCTIFS() becomes PRODUCT(FILTER()).
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Benefits of implementing FILTER:
Many present and future lookuprelated Excel UserVoice suggestions will be solved. See the link below
http://www.mediafire.com/download/m9tbv79sz61117r/SuggestionsSolvedBy_FILTER.txt
This means:
a) Less coding for the Excel team
b) Less waiting for users to get their IFS equivalent
c) The Excel team can focus on more important suggestionsReduces redundancy in Excel's function list and keeps Excel's function count to a minimum. This makes learning the functions less intimidating.
It sets a good example for future developers (decoupling, DRY principle, reuse).
It is already successful. Google Sheets already has it: https://support.google.com/docs/answer/3093197?hl=en
7 comments

Kenneth Barber commented
I don't know about everyone else who voted for this, but even though Excel doesn't have a FILTER function exactly like the one in Google Sheets, I am happy with the FILTER function that did get introduced to Excel, and I am willing to call this suggestion completed.
The next issue is how to handle complex conditions. This is what this suggestion is for:
https://excel.uservoice.com/forums/304921excelforwindowsdesktopapplication/suggestions/39976513addandandoroperatorsgoodforuseinthefilt 
Brian Dang commented
Microsoft PowerApps is the first place where I used Filter(). Once you get it, it will replace Index(Match()), VLOOKUP, HLOOKUP, and all aggregate functions that work on subsets. Conditions are built within the Filter() function, resolving any need for IFS, ANDs, or ORs.
If you have already done so, I suggest you try the Filter() function on PowerApps.

A.C. WILSON commented
Corey Becker's concern is an important one. Although I myself could easily adapt to a "FILTER()" function in Excel, my Excel files have to also be comprehensible by my fellow users, who might be less sophisticated than I. For that same reason, I need to avoid using array functions with {}, nonMicrosoft "AddIn" functions, and any tool that is not universal to ALL versions of Excel that may still be extant in my organization.
Some of my colleagues already have a hard time understanding my usage of INDEX(MATCH()) and of SUMPRODUCT(). [Of course, it doesn't help that the argument orders of INDEX() and of MATCH() are, confusingly, reverses of each other.]
[("Boolean thinking" is not universal, and, unfortunately, Microsoft's actual practice of explaining things in its "help" pages is getting worse, not better.]

Kenneth Barber commented
The link below shows how to do the OR condition in FILTER, so we don't need the database functions (e.g. DSUM) either.
http://webapps.stackexchange.com/questions/42428/googlespreadsheetfilterconditionorconditionsyntax 
Harlan Grove commented
FILTER wouldn't just replace the *IF[S] functions. It could also eliminate the need for *LOOKUP and INDEX+MATCH.
Consider
=index(filter(C1:C7,left(B1:B7,1)="A",left(A1:A7,1)="B"),2)
which in Excel would require the array formula
=INDEX(C1:C7,SMALL(IF(LEFT(B1:B7,1)="A",IF(LEFT(A1:A7,1)="B",ROW(C1:C7))),2))
to get the value in col C for the second records in A1:C7 with col B beginning with A and col A beginning with B.
As for worries about simplicity, 2 of the 50+ people I've worked with in the same office over the last 10 years have even known about VLOOKUP. Everything beyond COUNT, COUNTA, SUM, MIN, MAX and AVERAGE are for fewer than 5% of Excel users.

Kenneth Barber commented
Hi Corey,
Here are some additional points about FILTER that I think help my case:
1. SUBTOTAL is a function used by the general public for summarizing filtered results. The concept of separate filtration and aggregation would thus be familiar.
2. It's not just the IFS variants. Some aggregate functions have A variants as well. If all IFS and A variants were implemented, the function list would be triple what it needs to be.
3. FILTER does not require string concatenation for comparison operators. Comparison: SUMIFS(A:A,B:B,">"&C1) versus SUM(FILTER(A:A,B:B>C1)).
4. FILTER would provide compatibility with Google Sheets spreadsheets that use FILTER.
5. The versatility of FILTER should make up for the fact that it needs to be paired with another function to be useful (so I'd like to think).About your comment on VLOOKUP, it is not a function to look to for simplicity or robustness, only familiarity.
1. Why do you need to specify a table_array as opposed to just the 1st column? What is an approximate match? Does the col_index_num start at 0 or 1? These are all questions that I had when trying to learn VLOOKUP.
2. To search for multiple criteria using VLOOKUP, you need to do something like VLOOKUP(A1&B1,C:D,2,FALSE). To guard against column insertions in your table_array, you need to use VLOOKUP(A1,B:C,COLUMNS(B:C),FALSE). These are much tricker than the PRODUCT(FILTER()) combination.
3. There are many suggested improvements for VLOOKUP here on Excel UserVoice. People don't even like VLOOKUP.I'd like to think that FILTER would have, at worst, an implementation story similar to the Microsoft Office Ribbon or the Facebook Timeline. That is, the initial negative reaction turns into understanding and agreement.

Corey Becker commented
PRODUCT(FILTER()) would never be used by the general public. We all love INDEX(MATCH()) but 95% of Excel users have no idea what it is/does. But ask people about VLOOKUP and they'll immediately know what you're talking about. It needs to be super simple to use. It's a good idea but I don't think it could ever replace the list of simple IFS functions.