The Upgrade pack mentioned here is a VERY nice addition to the X-Wing Alliance game, and it makes the models look much cleaner. In fact, I always felt like after I applied the upgrade pack I was back to playing in the "true" Star Wars universe.
However, the upgrade pack does a number of things I don't agree with. It has a C version of the E-wing, which looks like crap, it adds in the Eclipse Star destroyers, as well as several dozen other Expanded Universe capital ships that severally unbalance the game.
And lastly, everyone with a model editor has created their own TIE Fighter variant with a ball cockpit and a smattering of TIE Wings that they put wherever just to be able to contribue something and frankly, most of the designs are just crap. I won't mention their weapons systems, but let's just say they could be considered capital ships and not have under-rated weapons systems.
Still, the Imperial Star Destroyers in this game (with the upgrade) have so much detail on them occsinally I have to convince myself they're 3D models and not the real thing. It's *that* good.
Also, I don't know if anyone played the CD version of X-Wing, but it DOES have an option to switch between re-vamped missions and classic missions, making some of the missions (Including the Redemption Scenario) a bit easier.
I also had trouble with the Runaway X-Wing mission. Mostly because it requires you to dogfight TIE Fighters and especially TIE Interceptors while flying a Y-Wing. I won't mention how insanely difficult that is due to speed limitations, but it's defeniatly of the Kill ship A before Ship B docks or Ship C will blow up Ship D...
On a more interesting side note, X-Wing was supposed to be developed with a difficulty setting for Hard Medium and Easy, that was never put in place. What this means is that on some missions, the enemy ships have three differant hyperspace entry coordinates. Including the Redemption Scenario. If you play the mission enough times, keeping track of the distances to the ships you can identify their entry coordinates. Of course, occasinally the enemy will drop out right where you don't want them and way to close to you, but that's just the nature of the game.
One of the missions that always gave me trouble was the Sullustant Diplomat mission, where you have to Identify the two transports with prisoners on them and disable them. Then I read the strategy guide, which told me which number transport they were if I just started flipping through targets in my CMD.