I like Tom Hardy and consider him a more than capable actor, but yes, I think if Stewart would have played the role of Shinzon, it would have been more engaging. For me, the dune buggy scene is the second most "meh" moment in the film, right behind the whole "prepare to deploy the tediously slow super destruction device!" scene with the Scimitar
There are some very good moments in the movie, but the bad does outweigh the good, just in my opinion of course. I just feel the whole movie was very indulgent, and as much as I love the TNG cast (and I really do), it felt more like they were just futzing around to run out the clock rather than doing any real story building. Again, just my two cents, because I know there are a number of people who really enjoy Nemesis
, and I don't want them thinking I'm trying to take that away from them.