I have been trying out the latest Tyranid list , and thought a few observations may be in order.

1) Objectives
Objectives are crucial to the Tyranids, and need to be placed as close together as possible. I placed my blitz opposite Hena's (slightly off-centre) and my Take-and-hold objectives fairly close to both of his.

2) Swarming
Bunching up is important to Tyranids to allow critters to be transferred between swarms in the End phase. However, this does allow the enemy to exploit flanks.

Equally, the Synapse creatures are key to the game - they are the only swarm creatures that can contest objectives, and also form the BTS objective.  

However, this all tends to mean that it is quite hard for the Nids to obtain "Defend the flag" and "They shall not pass" - and certainly virtually impossible against an able or knowledgable player.

3) Size matters
In two respects - the number of swarms is regulated by the cost of the synapse groups, and the number and type of critters available to each swarm is also very important. Hive Tyrants especially need other WE and AV critters in the swarm to soak up AT shots - but these tend to be in short supply because of the need to take independant formations to stand any chance of gaining objectives. So, you either have to keep the number of Hive Tyrant groups down, or use bigger synapse creatures (which are more expensive). Big independant creatures are also most usefull, verging on mandatory.

4) Style
The Tyranids play a little like the Siegemasters in style. If they can weather the first two or three turns, they can then try to grab objectives at the end of the game. The main point is that Tyranids are relatively immune to shooting and assault due to their size and re-spawning abilities, provided they stick together. Equally, the opponent is trying to isolate and destroy swarms and independant creatures one-by-one to reduce the ability of the Tyranids to win the game. In practice this very fine balance is as much down to army composition as game play.

5) Games
Against Hena, I decided to try a "Big critter" army to see if that proved over-powered, so three Hieraphants (275) and a set of Lictors (150) with two Vituperaptors, two Assault groups and a Hive tyrant, together with two Hierodules and a Trygon - Eight on-table activations with a third/fourth turn objective grabber, comprising 5x 6DC critters, 2x 4DC and a 2DC brood. See Hena's battle report here

The Tyranid plan was to advance the three Hieraphants close together to partially shield the Vituperaptors and Hive Tyrant, with the assault groups on each flank. The intention was to keep the five swarms fairly close together behind the advancing Hieraphants whose main role was to occupy the enemy's attention while the swarms occupied the centre of the table. I was happy to lose some Hieraphants and the Hive Tyrant as I thought the remains ought to be able to control the rest of the objectives - and was right, up to the last Marine activation.

I think the battle was a lot closer than Hena suggests, as I made a silly mistake (through tirdness) that allowed him to sneak the last of his two badly battered Landspeeder formations in to claim my Blitz and a T&H objective for two points, which I could easily have contested; while I was actually playing for a 4th turn. In the entire game Hena was only able to destroy one Hiereaphant, reducing a second to a single point, while the third advanced (broken) on his Blitz, despite using most of his army on them with a lot of clever cross firing. He did eventually manage to kill the Hive Tyrant towards the end of turn #2 which took out one of the two Hierodules, but both Vituperaptors were untouched from memory and both assault swarms had survived though one had lost two out of three 'nid warriors. So I was down to 6 activations with the Lictors to come in.

OTOH, out of 12 activations, I think Hena had the Predator anahilators, his supreme commander, three Landspeeders, a THawk and two formations of TBolts left - hardly likely to win turn #4

In practice, I would suggest that this Tyranid army was actually more than a match for a Marine force that was slightly engineered to fighting it, and would like to see how it fares against other races.

_________________
"Play up and play the game"

Vitai lampada
Sir Hemry Newbolt