yup, three times

Only about 5 times...

played ME1 an read the two books too before playing ME2

About 4 times.

" yup, three times "

I bought Mass Effect for the PC on Steam, thinking that my PC could run it with no problems (that's what canyourunit led me to believe...), and the performance is far from smooth; I won't go into the details, but it's not very enjoyable. So I decided that I wouldn't force myself to finish, and instead just get ME2 for the Xbox 360.
So... no
Yeah I'm in the minority I guess :P

I feel like a nerd. Over two dozen times between the PC and the 360.

I tried to finish it but student teaching got in the way.  Beat Noveria but didn't get any further.  Fortunately, that was my second character and my first is level 60 and ready to go when I get to play it after I am done at school today.

I've finished it once before but lost the damn save file. 
My attempt to go through it again in preparation for ME2 was scupperd upon realizing just how bloody linear the game is until you hit spectre status. If I have to go through Eden Prime one more bloody time...  >:| 
Ok, maybe it was my fault for trying to play each class when the first game came out. I just hope ME2 has some replay value.

" I've finished it once before but lost the damn save file.  My attempt to go through it again in preparation for ME2 was scupperd upon realizing just how bloody linear the game is until you hit spectre status. If I have to go through Eden Prime one more bloody time...  >:|  Ok, maybe it was my fault for trying to play each class when the first game came out. I just hope ME2 has some replay value. "

Beat it on the 360, but only one play-through. Anything at all doing with the Mako made my sigh in annoyance. Also, nearly every side-quest was the same boring repeating design over and over. I couldn't impress myself to try and push through it again. 
 
Regardless, it is a shame that when and if I purchase the game, it will be for PC. I don't really care about the bonuses, all the extra little levels and resources don't entirely mean much to me - the game does not end up being that hard unless you jack up the difficulty (at least as far as ME1 was concerned). I'm more wondering the impact of the choices made in the previous ME1 - the romance choice, the end decisions and other critical decisions. 
 
Anyone know how deeply they are referenced or impact on in ME2? I'm deciding whether or not to buy ME1 for the PC and just play through it once simply for the end-save file for choices.

I finished it last night about 1:00am (My previous save was stolen along with my Xbox so I had to make a new one)

I started Saturday at noon, played until 1am and then finished the game from 10am to 5pm Sunday.

About 7 times... Too bad I played so many different classes that not one of them is level 60. :/

i beat it 4 times, about a month before me2's release.  i wanted to finish all the achievements and refresh myself with the story.  i only wish i had paid more attention the story elements on my last play through as i only completed story elements with my level 60 character.  this game could be the death of me as i will probably want to run back through me1, complete all of the content as my badass paragon and then save the universe again in me2.

Played through the PC version twice, and due to a hard drive issue some months back I'm playing through it again at the moment to get a new save and of course to play through the game again. 

Once, about 2 years ago. For some reason it never grabbed my full attention. That may have something to do with just getting off my 2nd play through of oblivion and or due to the shitty ass drm which is still on my pc.

Yes, but found out I can't change my name so I'm now on to my 4th playthrough.

Did a Full Renegade, Full Paragon, Perfect Choices and now Perfect Character (Perfect Choices+proper first name).

I hate my perfectionist nature :-(

Yes, 3 times. But I lost all of my saves..... :(

Not yet, but when it comes out on Friday i'm going to buy Mass Effect 1, aswell as 2 and play through the first before i jump into the second.

Beat it twice, once on PC and once on 360.

I bought ME a few weeks ago and put quite a bit of time into it.  I got to the Ashley Kaiden part and chose ashley.  Little did I know that there was a know bug that sometimes would not let the player advance foreword.  That'll show me for not keeping an extra save every once in a while.  I'm almost back at Virmire again though.  I'll probably have to wait another day or two to play ME2 since I really want to finish ME first.  Even though I pretty much know what happens at the end. 

Yes, five times actually and reached lvl 60

I have, only once though.  I was still able to reach level 60, but I messed up some of the 'chievos since my party was constantly changing so every member had the same amount of party time, which led to me missing out on some party specific 'chievos.  As much as that annoyed me, I'm still more annoyed at the fact that when I sold my 250HDD I forgot to backup my saves to my MU and now I no longer have the save.  I really want the extra content you get when you import a LV. 60, but even more I want my previous choices to be imported as well.

hell yeah , playing the second without playing the first ruins half the fun.
 
Your decisions take effect on mass 2 such as  who and who didn't die in your crew for one.