(This is a second writing, so if it's weak it's because the first writing refused to save and I had to re-write)
As you probably know, these guys are my current army and I'm not too happy with them. The Tyranids, or 'nids, are the Warhammer 40,000 universe's "bugs." Science fiction needs its bugs, and all the bug characteristics are handled by the 'nids. You've got hive ships teeming with alien eggs, scuttling Gaunts invading ships and planets, Genestealers harvesting DNA for the Hive Mind, as well as acid blood, brain bugs, bilogical weapons...
The main cool thing about the 'nids seemed to be their cool look and their ruthless effectiveness. Yes, they look cool, I still have to agree with that. But they just don't seem all that efficient any more, not even Mark's. They have some extremely nice armor saves and some high-powered guns, not to mention some close-combat behemoths, but they've also got some severe lacks. The major lack is in the shooting department. Ever single Tyranid gun is short-ranged and lacks penetrating power. The run-of-the-mill lascannon, staple of all Imperial forces, can out-range the best of the Tyranids' many biological guns. Also, its AP of 2 can make a Hive Tyrant turn green with envy (after it takes its obligatory wound, that is).
What bothers me but probably hasn't even occurred to Mark or other 'nid players is that individual 'nid armies have no unique personality. You can't craft cool characters with neat bios to make your army truly your own. Every Hive Tyrant acts basically the same, because he's just a drone of the Hive Mind. This might not bother some people, but I want to be able to design cool characters to place on the battlefield.