I am pleasantly surprised.
The original X-Com was best known for its punishing difficulty. But it was also known, among people who played it much, for its annoying idiosyncracies and irritations. Xenonauts does away with many of these, simplifying things while keeping much of the difficulty. For example, you can define soldier classes that have no game effect, but allow you to set default equipment. Standard-issue gear costs nothing and takes up no space, because a base commander has better things to do than count rifle clips. Base defenses are automatically upgraded, because really, who wants to rebuild base components every time you research a new tech?
Some things are harder: The tech tree seems to keep things a little more out of reach, and funding is absolutely brutal. Some things are easier: Riot shields. Oh my God, riot shields. Instead of ablative rookie shields, lead your squad with a guy with a shield and a pistol. Why the hell didn't we have these in the original X-Com. It feels so good (and it won't help at all when a Chryssalid, or whatever they call them in Xenonauts, comes knocking). Also, if you crash an interceptor, your engineers will recover it and put it back together in a week or so. Losing an expensive ship near the beginning of the game is no longer painful enough to make you want to start over.
A personal favorite feature of mine is airstrikes. Are there four small crashed UFOs on the map at once? Do you need cash? Do you cringe at the thought of playing them all out? Just hit the airstrike button and the local military will blow it away, recover the scrap, and pay you for your donation...less than you'd get from a raid, but well worth the savings of player time. Also, intercepting alien ships is pretty rad. New dimension that X-Com never had, and it might not be your thing; you order your planes around in realtime, outflanking and gunning down the enemy with nifty fields of fire. Personally I could take it or leave it, but there's an autoresolve button, and since you can recover crashed ships it won't instantly ♥♥♥♥ you over!
If you've ever heard me complain about Galactic Civilizations II, you know I hate bad humor, especially in tech trees. I know...I'm weirdly specific that way. Well, your lead scientist in Xenonauts has an irritating intellectual superiority complex, but it's written *just right*, enough that you get a wonderful, subtle characterization just from the tech reports, no cutscenes required. You want to deck him in the face, not turn him off entirely. Well done, Goldhawk.
Anyway, I've played to the point where I'm through the first terror mission, and I gotta say there's a huge difficulty spike. Just as it should be. If you think the first month is too easy, take another look at your funding, and wait for some pain to roll into tactical. As a big fan of the original X-Com, I heartily endorse this game: Cleaning up all the annoyances and adding a few new features has truly made it new again. It's the game we loved, without the trappings of retro. Clear your calendar.