TxK [Vita].
tl;dr for the incoming wall of text:
It's pretty much a revised Tempest 2000, and that's good. Looks good, sounds good, but silly intermission tilt controls and can take a bit to start if wifi is on when loading the game.
But here's the wall of text anyway. Take note -- kind of not proofread entirely, and I'm too lazy to fix some of the more egregious errors.

==
the good==
* It's pretty much a revised Tempest 2000. We're starting on a high note.
* It looks great. Very crisp on the display. If you aren't afraid of possible epilepsy [some enemies flash the screen wildly for a moment when killed, looks tame in normal light, super fucking woah in the dark], play this shit with the lights off, screen cranked up to max brightness. You kind of get some of the feel of a vector display, which is nice [seriously, I remember playing Asteroids in the arcade for the first time ages ago after playing the Windows 3.1 port to death and being super amazed at the intensity of the lines and the burning bright shots of the arcade -- the latter isn't replicated, but the lines definitely capture it!]
* It automatically pauses and starts whatever MP3 you're playing if you adjust the BGM volume in settings to non-zero or zero respectively. Useful if you've got the Tempest 2000 soundtrack on the Vita and want to jam to that! ;3
T2000-5.mod [lower on page] is probably the best, render that shit in your MOD player with 50% stereo spread [the songs do make use of stereo, but hardpanning sounds awful on headphones usually] and bang it hard if you want.
* That being said, you may not want to use other tracks: TxK's soundtrack is badass. It's more synthy, unlike T2K's 1993-era hardcore techno soundtrack, but calls back to it a little.
* You can deathbomb like in Touhou to save yourself from getting pulled down. Only from that though, particle and beam weapons will just kill you without hope of recovery.
==
the bad==
* If you have internet on while starting the game, it'll take ages sometimes since it's trying to connect. One of the advantages of playing TxK over something else is that it loads super-quick, unlike literally everything else on the Vita.

That gets negated a bit if it doesn't immediately connect and the game is just spinning there while you wait.
* You can't disable tilt during the inter-round sessions, and if you're holding the Vita upright, they kind of don't work -- each round, the game tries to do make your tilt control relative to the position the system was in when the intermission started, but it only seems to work consistently when the back is perpendicular to the ground... There's joystick control, but it only works if the tilt direction isn't conflicting with the joystick direction [eg, system tilted to move left a bit, you're trying to move right == nope].
* It's maybe a little too subdued looking. We don't want Space Giraffe style effects, but the visuals are rather sparser than I'd hoped. The super-gradient style featured in T2K has made way for a flatter look in TxK. Mind you, TxK has a more involved look than T2K [flashing colors, more dynamic camera, more vectory, more particles because more processing power], but it does feel a bit flatter and some things don't seem to have the same feeling of "wow!". That being said, I know he said that he wanted the game to look a bit more subdued in
this post], so... [also, silly thing: that post won't load properly with TxK open and the browser at the same time!]
* There are yellow enemies that just fry an entire lane with the barest of warning [they stop for a second, and in the chaos of everything combined with the glow of everything get hidden]. If they flashed a bit before to be noticed, that'd be fine.
* I don't think there's an invincibility period upon death, or if there is, it's really damn short. Usually mitigatable [keep shooting, whatever is in your way won't be], but I have died a few times immediately after landing.
I got it for $7.99 since I signed up for PS+, and I think it's worth about that. It sells for $9.99, and I guess that's reasonable, especially if a few of the above issues get fixed.
I really enjoy playing it. It's always "just a bit further" or "just a bit better", and it's got the same kind of pick-up-and-play thing going for it that made Super Hang-On's 3DS port so good for me. Pick the stage you want, go on from there. Do a little or a lot, depending on how much time you have. Keep going with your score, or start from the top [with a separate board, something I wish SHO3DS would have]. Unlike all the rest of the Vita games I've played [which are effectively console games that you can bring with you -- I enjoy that, but waiting to load or trying to find a place to save is annoying], TxK is just a great portable game, accommodating both when you can only play for a few moments and when you want to play for ages.
I'd post this in the Vita thread or the TxK thread, but that'd be preaching to the choir.
So yeah, if you have a Vita, go buy it. Unless you don't like Tempest.