Tried locally on W8.1/64 and otherwise same ConTeXt and EBGaramond files I see similar issues (expect maybe kerning is done with new otf loading).

Three problems with ebgaramond.

• With the new otf loading facility, kerning is not done.
  
• With the new otf loading facility, the regular 8pt face is not found. If one is changing font size via \tfxx, the font size is not changed. If one is changing font size via \switchbodyfont[8pt], Latin Modern 8pt is substituted.
• With the oldotf module loaded kerning is as expected for the 12pt regular face, the 8pt regular face, and the 8pt italic face. The 12pt italic face, however, is not kerned.

%\usemodule[oldotf]% uncomment to see previous otf handling
\showfontkerns
\setupbodyfont[ebgaramond]
\def\Test{Vowel Tavern Tomato {\it Vowel Tavern Tomato}\par}
\starttext
\Test
{\tfxx
\Test}
\switchtobodyfont[8pt]
\Test
\stoptext

This was tested on W10/64 using ConTeXt  ver: 2015.10.09 21:28 MKIV beta  fmt: 2015.11.1  int: english/english, with EBGaramond files version 0.016 (April 2014) installed in C:\Windows\Fonts. Same results with luajittex (This is LuajitTeX, Version beta-0.80.0 (TeX Live 2015/W32TeX) (rev 5238)) and luatex (This is LuaTeX, Version beta-0.81.1 (TeX Live 2015/W32TeX) (rev 5442)).

Is this a problem with my font installation, or is it a general problem?

--
Rik