Vermillion:
I know I don't have all the answers, but I have flown the La-5FN almost exclusively since playing on AH.  Personally, I find the fighter quite within 
my perception of what it should have been like.  The only hard data I have on vertical and horizontal speeds vs. altitude is of the La-7.  However, in one of my books on Soviet fighters I found the following: a La-5F doing a combat turn would expect to gain about 975m.  The La-7 would gain anywhere from 1005-1220m.  The La-5FN would probably be closer to the La-7 in performance, since they both had the same engine.
As for my 
perception of the aircraft:
o given a little alt, the La-5FN can maintain a superior position against any of the aircraft up until about 20k.
o I have been able to pull away from all aircraft during the first minute, given that I started with at least equal E and didn't give my opponents too much height.  In fact, by keeping my opponents slightly below me and engaging WEP, I've even pulled away from Bf109G-10s for the first minute or so.  After that time has passed faster aircraft begin to gain, but slowly.
o The La-5FN does get mushy at low speed, but really hates to stall unexpectedly.  I've done numerous snap rolls on the deck at 150 IAS without mishap.  I have been told by Granger that the La-5FN has a higher stall speed than the P-51, but I want to test that out before making any conclusions.  Certainly, at speed it is no problem to turn inside a 51, or a 109.
o This aircraft is tough and durable.  I've been raked so badly by enemy aircraft that it seemed for sure I was goner, yet somehow she stayed intact, many times without serious damage.  Maybe its because of all that wood, but historically it was a tough plane too.
o The ShVAKs get the job done.
o The field of vision is excellent.
Vermillion, I've always been an e-fighter as well.  In WB I was always frustrated by the Yak-3s lack of offensive punch, but the La-5FN seems to fill that gap quite handily.  Nowadays, I just try to hold superior position then wait for the mistake and pounce - but always to hold the position.  One has to remember that with the exception of the Spitfire IX (a fabulously designed aircraft - genius really), the other two fighters are late war aircraft.  The La-5FN was an early to mid-war fighter, coming out about the time of the battle of Kursk.  It should be very interesting to see how the La-7 will do when/if it makes its debut here   

Edited this last note - Verm, I don't use hammerheads, but I do use combat turns (like a chandelle, where after the turn you hold the height gained) and hi and lo yo-yos.  Oh jeez, it just hit me!  I fly the La-5FN like a 109!  A long time ago I flew the 109K in WB as -batu-.  Always loved that form of aircombat.  The hi lazy stoop, then the bounce, followed by another hi lazy stoop.  Usually I wait for the enemy to shoot their wad trying to reach me, then pounce on them as they stall.  Exactly what I used to do in the 109.  Man, when the Soviets built this plane to beat the 109, they beat it by its own game!  What a revelation!
Verm, fly it like a 109.  I do.  It works.
[This message has been edited by leonid (edited 10-20-1999).]