I just got around to playing this, but... Well, the H content was quite good, everything else was honestly pretty mediocre.
As far as gameplay goes, it was simply tedious. You face the same three enemies constantly (occasionally with a pointless side of infantry), which you'll deal with in the exact same way each time. Regardless of actual mission objective, you're generally going to aim for full clears to farm parts. So far as I can tell, there's only one mission that even has anything approaching a time limit. It's never hard - it just feels like everything takes longer than it needs to.
In terms of progression, the advertised upgrade system is extremely lackluster - your only real choice is whether you're going to get a small amount of attack/defense, or more uses for your special bullets. It looked more promising at first, when you also could choose from mine detection and civilian rescue, but those were the only two that meaningfully expanded gameplay. This same issue extends to contribution points, where you're just given new weapons and armor automatically; personally, I think it would have worked better as a proper store, giving you more freedom to focus on parts that you cared about, or even allowing you to buy enemy cores in lieu of new weapons. Certainly, for most of the game, I'd have preferred more explosive rounds over a new assault rifle.
In terms of plot, it started off interesting enough, with a shady-yet-vaguely-decent company deciding to support the main character's revenge in exchange for the chance to lewd you later, but... It kind of falls off a cliff from there. On a lewd route, it just serves as a pathway to the game's H content, while on a pure route, it just never goes anywhere at all. I'm not asking for anything deep, but it would be nice if the characters we were introduced to were more than just window dressing - or at least had more than their introductory dialogue. This extends to the evil organization you're destroying, who were barely described - like, after the fact, we were told they each played special roles in the organization, but that never really showed up at any point... And we're never really told why they're smashing everything up, either. It kind of seemed like they were after generic world domination, but it never really seemed to tie into anything they were doing, nor explain what they did to your hometown. This really weakened several important points of the game - namely, why the intelligence gathering specialist became obsessed with defeating you to the point that she put herself in danger, why the cruel treatment of the captured commanders was remotely justified (frankly, it made it feel like you were playing for the bad guys), why the main character has such a grudge against them, or why they even left Europe to attack Japan to begin with.
In terms of exploration, it was nice to go around and talk to everyone... The first time. But contrary to the game's implication, nothing actually changes unless you wear the H-suit. You'd think that at the very least, the other pilots wouldn't treat you as a rookie after capturing three commanders and having 80+ popularity, but... Nope, everyone says the same thing as they did at the start.
Except when we get into the H-content, which was treated much better; here, we see new areas open up as you get more involved in lewd things, and those areas change in response to your actions. Magazines are sold with your fashion shows, ads you starred in are shown on displays, people recognize you from things you starred in, and stalkers show up after you give them enough leads on where your house is. None of these areas are large, but most of them feel like a pretty good slice of what your life is like now - if they'd have extended the same treatment to the non-H portions of the game, I'd have called it a great game, even with its other shortcomings. As it is, however, you're not even allowed to go home unless you use it to star in a porn shoot.
Which brings us to the H-scenes themselves; these are frankly well done. The main character has a very natural progression from feeling somewhat uncomfortable with Underground TV, to really enjoying her new role - and all of the scenes along the way do a good job of being a bit pushy without wishing that you could just flip everyone the bird and walk out. You have a pretty good variety of scenes as well, so if you dislike one event chain, there's likely another that better suits your preferences. Many of the scenes outside of Underground TV are more hit-or-miss, but they're pretty much just a bonus to begin with.
If I had to make a complaint about the H content, it's that it's rather self-contained; the only point of intersection with the rest of the game comes in the form of your commander (aka the president's toy), and the guard checking your ID. No one else in the company either takes part in your increasingly lewd adventurers, nor takes any note of them. This kind of makes me wonder if they had originally planned more before deciding the scope was getting out of hand - the designs of both the mechanic and the person giving you missions feel like they were originally intended to have scenes as well, but, well, they don't. Then again, it could just as easily be that they didn't want them to be generic NPCs considering how often you see them.
Overall, it's somewhat frustrating, because I want to like the game, but... It ends up feeling pretty shallow outside of the H-content. And I really need more than just good H-content to like a game.