I think tunnelling visitors at this stage is vital regardless of who they are, my second biggest client is a Technology retailer who has real problems with wandering users.
When we started doing user studies we found that a good portion of visitors took more then 1 day to complete an order, with many going right the way up to the confirm my order stage before holding off and coming back.
The reason simple they were checking the total price, must people don't give accurate shipping or VAT details at the beginning so another good piece of advice is to add the VAT and shipping charges information when users view their shopping cart rather then waiting till they start the checkout process.
Storing customer info is another area you may wish to look at, many sites try to force registration on shoppers, I would say that breaches the golden rules
if its not needed don't collect it, if it is not vital and can be collected later collect it later
A nice idea is after customer has placed their order the first time and its been completed is to then offer registration (to help conversion you could make features such as sending SMS messages to them part of the membership)
Being able to login and place an order quickly is great for repeat users but not everyone will be back, so avoid compulsory registration where possible.