I ran into something loosely similar a while back with my Eldar and it caught me totally off guard. I say similar simply due to the sheer number of lascannons. It was a battle-company with 9 Lascannon Razorbacks and it really threw me for a loop. Sadly didn't get to finish the game but my army was in tatters by turn 3.
My list was NOT totally optimized and when I faced it again later I trashed it simply due by avoiding firing lanes and maintaining cover through battle-focus. But the big difference was he was using Razorbacks... not Space Marines on foot.
I think it can definitely work against a lot of armies and should be able to handle Knights fairly well. The key will be deployment for and establishing fire-lanes, and also when/when not to combat squad. I think its a very cool list and I love the presence of plasma for anything that gets close. You can also move out and clear mid-field objectives.
However anything holding objectives in your opponents DZ will be a problem. Armies like Necrons who can shrug off lascannon fire with high mobility, multi-wound assault units with invuln. saves like Wraiths will also be a problem but thats the case with any "extreme" builds (I only label your list extreme, in that its so spammy, not crazy power cheese or anything). I think its totally worth playing in a few games, and a list I'd hold on to because I think it'd be a blast to play and quite effective. If you manage to get a few games in let us know, I'd be fascinated to see how it does.