With Personal Force Field on you can only use powers that affect yourself, so no buffs on your teammates, or attacks on your enemies. Even toggle buffs like Dispersion Bubble and the Leadership Power Pool will only affect you while PFF is running. However, with PFF on you will be insanely difficult to kill. Put 3 defence SOs in this power and you will have a defence far exceeeding 100%, as well as very respectable damage resistance against all damage types.
Using this power I have taken the alpha strike from large +2 Nemesis mobs, taking less damage than my Invuln Tank would. PFF basically fills the role Phase Shift used to, before that power was given a timer with Issue 5. With my lvl 50 FF Defender, I can honsetly say I can only recall dying two or three times with PFF running, the greatest risk being from mobs that get a hold or stun through, dropping the toggle. Straight up damage will almost never kill you though, provided you're not fighting +8s or something.
Also providing you get both the targetted defence buffs (you really have to get these, people expect damage mitigation from a Defender), you are going to be much more squishy than the rest of the team, with less than half the defence that you have provided them with, seeing as you just have Dispersion Bubble and maybe some pool powers providing some protection. Against an enemy that throws around a lot of AoE damage, your health bar will go down much faster than the rest of the team, even if you're not drawing aggro. This is one time when PFF could be used, in addition to its common use as a panic button or while travelling.
Dark blast is a excellent choice for a Force Field Defender, as the -acc debuff in the blasts can further reduce the attacks landing on your team.
Really?
My Leadership and my dispersion bubble still gives it's buffs to my team... which i'm really grateful for.
My Forcebubble doesn't work or the closer range knockdown bubble though.
But the other 2 definately do still work.
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I know what you mean, i've been on a team often enough where i go flying ahead to see what's on, get in trouble and then PFF and just hang there getting shot at by reds/pinks/oranges and taking little to no damage.
It's quite fun! 
Are you sure dispersion bubble is buffing your team and not just yourself? All accounts I've heared indicate PFF blocks this.
With PFF on you can: click glowies & travel in relative safety.
I really should do something about this signature.
Yep, i'm sure it's still buffing them, I'll double check it tonight.
I know for a fact though that my leadership defence is working through it.
I wish my force bubble was too though.
Ahhh to sit in safety while no one can get a close shot against you and have to use their ranged attacks.
Anyone notice, but the forcebubble draws a lot of aggro, at least for me... and MAN do those ranged attacks hurt, specially when teaming with people a few lvls higher.
I digress though.
The PFF is definately a FANTASTIC power.
It's the only thing that's saved me from loads of debt on more than one occasion, although I really should click it sooner, that split second seems to get me everytime though.
And then it's off to the hospital.
The PFF is really one of the major things that makes playing my bubbler so great!
Right then, that's me told. PFF it is!
Primarily I want to build a defender for pretty much exclusive team play, so I've taken both of the first 2 FF powers and the first 2 dark attack powers by level 4. Seems to be OK so far, and I must say the PFF is great for travelling around and I'm looking forward to see how it does in the hollows with all those orange and red types constantly taking pops at you while you try to find your door missions 
i remember with PFF on my troller i could cross the gulch in safety when i was just a mere lvl 6
bout disp bubble and leadership.. you can activate them but they will only buff yourself and not your teammates. I always leave disp bubble on when i fire PFF, just to add another extra bit of def.
"god, how many devs did hami have to sleep with to get ED?"
Total Cat @Stagefright
Indeed you can, and I'm very impressed! I crossed the gulch several times last night with my PFF buzzing away and no problems whatsoever - so of that at level 5... Pity the same could not ne said for the rest of the team 
Infact I'm very impressed by the FF set altogether, and it's fun to play a buffer rather than a fighter Funny how mistaken I was when I looked through the powerset . . .
OK, so with PFF on you cannot activate Dispersion Field and have it affect your team mates, but what if it was already on when you activated PFF? Anyone know?
Same thing I'm afraid... does not affext your teammates.
yup, it just disables any ally buff it was giving, and transfers it to only you being affected. So I recommend you get a keybind or something to say you're firing PFF when you got a team in your disp bubble, so they dont falsely assume they are safe in the bubble .
"god, how many devs did hami have to sleep with to get ED?"
Total Cat @Stagefright
What exactly can you do when that is active?
I'm looking at the forcefield set and it doesn't seem to offer much in the early game. Am I missing something here?
Thinking of teaming it up with Dark Blast.