I sat on the fence all day yesterday before pulling the trigger on Mark Studio 2. My wife talked me in to getting it. I have used Audiffex GK Amp Pro 2 exclusively since it came out and pounced on the 64 bit upgrade for it.
My main guitar sim has been the full version of Overloud's TH2 since trying the Producer version when it came in Sonar. I have to say Mark Studio 2 has dropped my jaw! This thing is incredible!
It's only half price until 12 midnite tomorrow so if you have the extra cash this is a no-brainer!
WORTH EVERY CENT AND THEN SOME! 

I bought it awhile back from someone at KVR. It's a very nice one to have. Between it and Amplitube Ampeg...I'm pretty happy with my choices for bass.

Thanks for that! I wasn't planning to buy anymore stuff but this is the perfect complement to my bass amp and it's a lot cheaper.

I use Mark Studio and Scarbee Jazz bass on all my tracks and the realism is amazing! The different sounds are awesome.  One thing you may want to try is adding a breverb patch called Bass Room (I believe) on the track.  The room reverb on Mark Studio is a little too large for my taste.  Adding the bass room patch adds just enough space.

I played around with it last night and it's much better than I thought it would be! There's a huge variety of tone. Now I want to trade in my hardware Little Mark for a TA-501. The TA-501's two additional mid range controls make it very easy to dial in a good tone. Definitely worth it, for me anyhow.

This has to be the first time I've ever seen a person want hardware based on a sim. IT's supposed to be the other way around. 

It's that good!! 
 
Seriously, I use the 'real' amp much much more than I record. The tone controls on the LM emulation react very much like my real LM, so I'm assuming the TA-501 emulation is accurate too.

dlesaux! I use Scarbee Jazz bass also when composing at the keyboard. I love it. But, before I wrap up the project I have a Fender Jazz Modified Fretless Bass that looks like Jaco Pastorius's bass. I can't wait to lay some tracks now with Mark 2!