This is a fine, maybe even good game, however it falls short of a great game due to the horrid scrolling. The option to control a turret is great, but you can't use it well at all because you can't scroll practically while using it. Needs better controls, and until then, 3/5.
1551 kills on extreme!
For those of you who haven't figured combos out, follow - http://onslaught.playr.co.uk/about.combos.html - for the list of combos, and when placing turrets, hold 'C' to see if your turret is in combo range. If you decide to switch your combos up, you can highlight a turret, and press 'M' to move it.