Definitely. Omega Five may just be the best beginner shmup ever. It's challenging for a beginner, but still easy enough to be highly doable. Should be a fantastic warm-up for Ikaruga and Triggerheart Exelica for people who aren't used to the genre.
Sadly, this means that the game is way too easy for an experienced player. I've cleared the game without dying three times in one afternoon!
Here's the list of unlockables I know of so far.
60 minutes = 5 credits
90 minutes = 7 credits
(I believe this is effective playtime as I've left my machine on while I go do other stuff all day. Also, I assume 120 minutes is 9 credits and whatever beyond that is freeplay.)
Beating the game with dying = Challenge mode.
Beating the game without dying as...*
Ruby = R.A.D. (second female character), Arcade++ and Challenge++ mode.
R.A.D. = Female announcer (yes, she is as funny as the male)
Tempest = Sensei (
I'm talking to you, Birdie!)
Sensei = "Retro mode" (I don't know what this is yet. My friend told me about it.)
* It's possible that it's not for specific characters, but just 1st, 2nd, 3rd and 4th times regardless of character. The order I listed them in is the order I beat the game without continuing.