Let me offer an alternative viewpoint. In over 800 laparoscopic cases, I have felt the need to use the Hassan technique in only three, and all were in various stages of pregnancy at the time. I have always used the Veress needle exclusively. My bowel injury rate is zero. I have had to convert lap chole's for the usual technical reasons (difficulties, not complications), have had to open two cases because the sheer density of adhesions prevented development of an adequate space, but have not had to open for access.
1) a sharp needle. Some of the re-re-resharpened ones just aren't as effective. Not a slight against reusables - I use them - but quality is an issue.
2) avoid the problem area - the midline. During a laparotomy, one avoids adhesions in entering the abdomen in order to avoid injury. Why relearn the lesson laparoscopically? Insert your needle at the site for the midclavicular port. Or further laterally. Lift up the midline, and direct the needle perpendicular to the wall. The sensatiion is not quite as "crisp" when inserting the needle, but is nevertheless distinct.
3) If you have to use the Hassan, avoid the midline. Nothing like reading the reports of "how we used the Hassan to avoid injury" - then went through the midline, and into the transverse colon anyway. Why look for trouble (adhesions)? Stay away.
Not scientific, perhaps, but certainly effective. My three partners' experiences mirror mine. None of us have any experience with the Hassan. One has used the dagger-like trigger assembly which the camera slides down, from US Surgical. He claims success, but it seems like you would just see yourself entering the colon up close and personal, rather than avoid the bad stuff.