On the 4th December Opera launched the first alpha of Opera 10.
A month later I have opened this blog using Opera 10 / Kiwi Linux to see how each counter reports this.
OneStat: Other / Linux
SiteMeter: Default 10.00 Opera/10.00 (X11; Linux i586 ; U; en) Presto/2.2.0 (This visit does not count against total browser numbers, Opera 10 is obviously not among SiteMeters known browsers).
StatCounter: Opera 10 / Linux.
GoStats: Opera 10 / Linux.
log24: Opera / Linux (Log24 lists Opera 9 as Opera 9).
eXTReMEtracking: Other / Linux.
Motigo: Opera 10 / Linux.
So full marks to: Motigo, GoStats, and, StatCounter, plus a commendable result for log24.
This test shows either the flexibility of a counter, i.e. being able to create a new variant from the information given, or that the counter is maintained efficiently, with new variants being added soon after release.