Outing myself as a huge nerd here, but from the caps I've seen the biggest issue is that they've changed the iconic title and typewriter-style fonts in many of the episodes! I've spent the last few months rewatching the series on DVD (have just started slogging through season nine, much of which I've never seen before) and can't imagine upgrading - the various edited-on-SD-video effects are part of the whole retro aesthetic, surely? (And presumably "X-Cops" is entirely upscaled?)
I loved the series to death as it originally aired (in my early teens) and was amazed how much I remembered of episodes I hadn't seen for nigh-on 17 years, as well as how many of the later ones I'd never seen. My main take-aways from watching it through:
- Yeesh, Mulder is such a douche through most of the series' run. Doggett's warm sincerity is really quite refreshing after Mulder being a diva for seven seasons.
- The hoary voiceovers that open all the mythology episodes are awful.
- I remembered season 6 (and the move to shooting in LA) as really being the beginning of the end but on rewatch found it one of the more consistent and purely enjoyable seasons, with the amped-up comedy working more often than not. Of course that all goes out of the window with season 7 (where Duchovny mainly phones it in and the show just seems tired), but still, nice to be surprised.
- Vince Gilligan was (barring the obvious exception of the great Darin Morgan's all-too-brief reign) the series' MVP and most consistent writer - after a wobbly debut with "Soft Light", pretty much any episode with him writing solo is a highlight of its particular season, or at the very least never dull.