Things from shop that cost money so should be bonuses in fact make game harder.
Great game! Reminds me of Kirby avalanche (or ghost trap). Tetris-theme battle is nice and everything else bundled in just made it better, mainly, the combat above and upgrade mechanics.
The main fun from the game is those pesky combos that aren't anticipated (they can't be since the pieces are off the board). I just got a 6-combo on my first play, on the first level out of pure luck.
Anyone claiming this game is boring just don't like the theme. It's not boring. Otherwise 99% of all strategy games, both video and board, are boring.
I really enjoyed this game.
The only things I would change, though, is have more songs (the one played during battle got old quickly) and to put a difficulty rating on each battle, so you would know what you were getting yourself into.
It's a good game to have on the NinDS if you ever consider porting it. Not everyone's cup of tea; if you're bored of Bejewelled chances are you won't be entertained by this longer than 5 minutes.
Graphics bring back nostalgic memories, and the music's 8-bitically awesome though repetitive after a long duration. It would be cool if I could still swap my units while the combo break is happening, which would contribute to general game pace. A quick tutorial for beginners would be good. Like, which board is yours and the AI's, where you can upgrade, etc. considering how it could be some people's first time playing a match-3 no matter how uncommon this situation can be.
Adding in occasional cutscenes, even if just a simple pixelated comic page would be interesting, too.