First of all, I consider myself neither a Lucas-fanboy, nor a die-hard SW-fan, although I grew up with a lot of Star Wars in my life. Of course, I have only seen the OT on video (I am 23 now), but since then I was a fan not only of SW, but of visual effects. Over the years I got a quite notable collection of Star Wars books and toys, and even now, four posters of the non-SE trilogy are the only posters in my room. Of course, I was really thrilled when I learned about the SE being worked on, and it became my first opportunity seeing those movies on the big screen. And being an effects fan I generally liked the additions to the trilogy, including the extended Mos Eisley shots and the discussed Jabba scene.
I guess it's hard for me judging how the Jabba scene modifies the pace of the movie, since I have seen the movies so many times (and being a huge Harrison Ford fan, with Han being my absolute favourite character in SW), so that I am just happy to see MORE Star Wars (and Han) than before. Now, taking a step back and looking at this particular scene, I've gotta admit that Klingon_Jedi has a few points that really make Lucas' statements appear false. Generally I don't like Lucas since I have watched the "From Puppets to Pixels"-documentary on the EP2-DVD. I don't really know what it is, but this docu really makes me mad at Lucas. I didn't really think about what he said about the Jabba-scene, but now - with Klingon_Jedi's post as a remainder - it doesn't make sense claiming it being planned as a VFX shot.
Jabba being a slug, or an alien of ANY kind wasn't planned before ROTJ, that's for sure. Otherwise there would've been sketches of him in some publications dealing with the design of ANH. Second of all, Klingon_Jedi's right, the way the scene was shot, it could've NEVER been made a VFX-shot. And Lucas knows that. In "Empire of Dreams" (yeah, of course I own the new DVD-set *g*) it is shown that Marquand got help from Lucas on several shots requiring visual effects to be inserted, so Lucas really understood how a shot like that has to be set up. I've worked on a few commercials and industry-films, so I know about compositing and matching effects to moving footage, and there is NO way a stop motion figure could've been inserted into the Jabba shot back in 1976. So clearly, that's not the reason it got cut out.
A similar "inconsistency" of a Lucas-statement came to my mind when McQuarrie talked about his design-idea for Vader. He had the idea for him wearing a mask, because he had to swap ships in space. On the other hand Lucas always claims, that he had written the whole story of the saga even before ANH got shot (and probably before it got designed), including the reason why Vader wears his mask (the lava-pit and stuff). So, either it was a GIGANTIC coincidence that McQuarrie gave Vader a mask, OR Lucas lied. I might as well be absolutely wrong here... maybe the first draft of the Saga didn't mention Vader's past at all... so, this is just a thought.