Ok ... I just finished my first Insanity playthrough a couple days back and ... wow.  I can't remember the last time I felt such a sense of achievement in a game.  Wow that was tough but I now see the GENIUS of this game's design and this unquestionably is the game of the year and this series the defining one of this generation.  PS3 owners BETTER take note and embrace this gem.

Ok, some details:  I played NG as a Vanguard.  First 2 playthroughs on Veteran as a Vanguard and Sentinel.  A Vanguard on Insanity was deemed insane by many but just wow Wow WOW was it a satisfying thrill.  I came to see how WRONG and SLOPPILY I was playing the game before.  So amazing how good I got as I started to see and by time the Collector's Base came up I was taking Samara and Kasumi just running over Harbinger and all commers.  It was a great, great time.

Next up will be LotSB and whatever the next DLC is.  I'm going to wait so I have more to play than just the one pack.  ME demands long sessions.

I plan to. Just give me a damn release date, Bioware.

What is a good class to play through insanity with?

Any of them can work, but believe it or not the Vanguard really shines in Hardcore and Insanity in particular. You die easy, but you kill enemies so fast it's almost painful to watch.

Painfully awesome.

I love the Arc Projector and the Collector Beam weapon, rarely use the others...except the Nuke gun, used that on the final boss on my first playthrough, easiest boss battle ever with that

This is probably a silly question, but what's the hardest class to use for an insanity playthrough? I played an Infiltrator for my Hardcore playthrough (with Reave as my special ability) and it was honestly easy once I was able to use the anti-material rifle. 

From Bioware forum about the PS3 version

"-An interactive comic retelling ME 1, that you will make the key decisions in.
-It'll include all previously released DLC. (Which is a given)
-And it'll be have a new 6 hour mission / DLC. I don't know if that's exclusive to PS3 though. If it is, I'd imagine a huge backlash, but I reckon if it is true, it'll coincide with PS3's release."

The frame rate in this game was horrible. I could not force myself to finish it and sent it back to gamefly.

The answer will probably vary between each individual.

In my experience, the vanguard has a difficult time in the early parts of the game (because you don't have the powers and upgrades to survive easily in close-range yet) but once you get to Horizon and onward, the vanguard class starts becoming a monster, where you'll start charging Harbingers, Scions, and even Mechs.

I feel the adept is also similar, in that it has a bit more of a difficult time in the early parts of the game (since the cooldown of your abilities aren't shortened yet), but becomes an absolute controlling powerhouse towards the latter game.  You'll often hear people complain about why powers can't work on enemies with defenses (armor or shields), but honestly, a few shots with your weapons (or with the help of your allies) is enough to strip defenses and start throwing out singularity/warp explosions.

In my opinion, the easiest class by far is the soldier.  Soldiers excel at pretty much any combat range, and Adrenaline Rush can be incredibly powerful with several weapons.

I will admit that the only difficulty level that I have played Mass Effect 2 on is insanity (thankfully you don't have to unlock it like how you had to in the first game), so I don't know how the classes differ on easier difficulty levels.

You're talking about Mass Effect 1 right because 2 didn't really have any framerate problems