Allow me to chime in -- now that my account is finally "fully functional". To me, Tom Paris is one of the (if not THE) most multi-faceted characters in ST. He is pretty much the only one with more than one job, pilot and medic -- not to mention shuttle designer; he has several hobbies that turn out quite useful, to wit, holoprogramming, 20th century history, and car mechanics; he gets into and sustains a lasting relationship; has a child; and did I mention he's the only one who actually CHANGES during a series, and has a genuine character arc? So yes, I think they used him well; I've called him the true Voyager of the series.
Someone earlier said he wouldn't fit into Starfleet. Well, after the demotion he really does his darndest to do just that, and earns -- literally EARNS -- his rank back. (Remember "One Small Step", just as an example?)
For all the above reasons I've made Tom Paris the focal point of my own post-Endgame story series (yes, I admit it -- I'm a geeky fanfiction writer, stopping short of erotic dreams though). He's tremendous fun to write. And yeah, I wish the writers had done more of that, but if RDM didn't get a ton of lines in each and every episode, neither did the others; it's called "terms of contract".
Cheers all, and happy to be on BBS!