Sorry I can't answer the questions...except to say have a look at what ligatures are included in commercial fonts.
I noticed you need to merge contours on the italic Q :)

Regarding Polish diacritics all but Ł and ł (uc and lc slashed L) are really well drawn, which is not common. Without Ł and ł (uc and lc slashed L) you cannot typeset texts in Polish language. There's also historical and rare ligature combining to lc "łs" link to example of ligature łł. BTW very interesting typeface.

Cheers,
Antoni

You might find Thomas Phinney's blog page about Extended Latin character sets useful too. It is mostly about varying levels of language support, which isn't exactly what you're looking for, but it might keep you from working harder than you have to. You have probably already seen it referenced in another Typophile thread though.

Thanks for all the comments everyone.

Ben, I am still doing some fine tuning of the curves and I haven't decomposed all the characters yet so a few of them do get knocked out when they overlap.

Antoni, I do have a Ł and ł. I don't know if you saw them or not. They are up near the top of the file in a section called "derivatives". From what I read I didn't think they were diacritics and I didn't know exactly how to define them, so they got group with other slash or bar characters. If you did see them but thought they were designed incorrectly, I would appreciate some specifics.

Jason, it has been awhile since I have seen that page. I kind of forgot about it. Thanks.

Silly me, haven't seen these. They're fine. I'd like to see this font printed on a nice uncoated paper someday. Hope I will,

Cheers,
Antoni

The typeface looks quite interesting. The important omitted glyphs are as follows:
Idotaccent (uni0130) and dotlessi (uni0131) (Turkish, discussed here)
Tcommaaccent and tcommaaccent (without Unicode reference, needed for Romanian)
Eng (uni014A) and eng (uni014B) (needed for rare languages like Sami and some African languages)

If becoming punctual, there are also 4 optional glyphs you should add, although in many typefaces they are not present - Aringacute/aringacute and Oslashacute/oslashacute (although I'm too lazy to check the Unicode points for them).

Also from WGL4 maybe you should add kgreenlandic (uni0131) and napostrophe (uni0149), although I haven't seen them in real use.

The matter of adding CE charset is discussed in more detail here.

Now about the quirks: I have some doubts regarding the ogonek placement in iogonek (Roman). Otherwise the diacritics placement looks ok to me.

Thanks Asparuh.
I added the Idotaccent and dotlessi.

I have a Tcommaaccent (uni021A) and tcommaaccent (uni021B), but I don't know what you mean by "without Unicode reference".

I am now working on an Eng.

Does anyone know what languages the Aringacute, Oslashacute, kgreenlandic and napostrophe would be use in? I can't find any information that make me believe they are needed any longer.

Aringacute and Oslashacute are almost obsolete, although still are used in some Danish grammars, dictionaries and other linguistic texts, perhaps also in some poetry (quoting John Hudson from here). kgreenlandic (aka kra)and napostrophe is almost extinct, but I still see them often implemented in many typefaces. They are described in this PDF by Michael Everson. Implementing it possibly would require to add also a specific Greenlandic uppercase K, as described here.

About the lack of Unicode reference of Tcommaaccent the mistake is mine (in my old FontLab codepages I found only the glyph name, not Unicode values). Should have checked more thoroughly.

None of these glyphs are in heavy use; I mention them only because they still exist in WGL4 specifications (i.e. Microsoft cosider them still not totally extinct).