I wouldnt have any hesitation in using the net to book holidays. It is always cheaper.
The trick is to go into a travel agents and let them find you a nice holiday. Then when they give you the print out, find the same holiday on the net and book direct.
I went into a local travel agents branch and our holiday to Goa was £1,400 - the one that I liked. The print out said it was with Manos tour operatour. I came home, and found the identical holiday on the manos website direct for 400 quid less. The travel agent obviously needs to make a commision.
I used manos/airtours/mytravel a few months ago again and booked a holiday to mexico. I'd certainly reccomend them. They do direct flight holiday packages from manchester to thailand, goa, cancun etc but at prices not much more than spain. www.airtours.co.uk