You bet even odds. Does this mean you are equally likely to expect a Higgs as not, or simply that your belief of there being no Higgs is equal to that of RolfAndreassen's belief that there is one? Genuinely curious here.

The odds (and size of bet) were proposed by the other party. So all you can deduce is that Eliezer thinks Pr(Higgs)<1/2. (If you have a good estimate of Eliezer's risk aversion level for bets of that size, you might be able to get a slightly better estimate, but my guess is that it's extremely close to zero.)

Yes, that's why I asked him.

At this point I'd probably bet 10:1 against the Higgs, even taking into account risk aversion.