I've been reading the other thread, but it's for UK passport holders.
I have an EU passport (non-UK) and I have a US B1/B2 visa ('tourist visa'), so from what I understand, I don't need to have an ESTA, is that right?
But I will need to fill out an I94? Is it the same whether I go by land or air?
Anything else that I'd need to do to get back into Canada without any problems (I have a SOWP)?
Thank you.

Which countries participate in the Visa Waiver Program?
Andorra Estonia Ireland Monaco Singapore Taiwan[1] Australia Finland Italy
Netherlands Slovakia United Kingdom Austria France Japan New Zealand
Slovenia Belgium Germany Latvia Norway South Korea Brunei Greece
Liechtenstein Portugal Spain Czech Republic Hungary Lithuania
Republic of Malta Sweden Denmark Iceland Luxembourg San Marino
Switzerland

The Visa Waiver Program allows foreign nationals from certain countries to travel to the United States for business or pleasure, for stays of 90 days or less without obtaining a visa. Travelers admitted under the Visa Waiver Program must agree to waive their rights to review or appeal, as explained in the Waiver of Rights section of the Application screen. See Who is eligible to apply for admission under the Visa Waiver Program? for further information.

https://esta.cbp.dhs.gov/esta/

NB: Visit visas should generally be applied for in a country of which the candidate is a Citizen or permanent resident. Applications made in other countries often run a high risk of being turned down. The most common reason for refusal of B1/B2 visas is the applicant showing insufficient evidence of social, family or economic ties to his/her country of residence that would ensure that s/he would return there following the visit to the USA.
http://travel.state.gov/visa/temp/types/types_1262.html

It makes it easier if you have a visa, no, you don't need to do ESTA, CBP are required by law to use your visa category if you have one, they cannot use the VWP.

How it works if you have a visa is that they swipe it, the I-94 is automatically generated, you just give them the address where you are staying and they fingerprint and photograph you (US-VISIT). Also the fee is $6.

The only difference with air travel is that the processing fee is included with your ticket.

Whichever country you come from, if you have a valid US visa in your passport then you don't need to have completed the ESTA.
When you land with the B1/B2 they will ask you to fill out an I94, it will be the same procedure whether you're arriving by air or at the land border- you'll still be given an I94 to fill out. In terms of getting back into Canada you won't have any problem at all, especially if your Canadian visa/work permit is valid. Good luck!