Dimensions off on final part I'm experiencing an issue with my Makerbot Replicator 2X (2000+ hours printing). The dimensions of my final part are smaller than what is initially modeled. My parts have been coming out roughly 0.3mm smaller than what is initially modeled. Is this a common issue or does this sound more like I may have a hardware issue?

I've confirmed that all my belts are tensioned properly and lubricated correctly. I haven't seen a calibration step that would correct for this issue short of manually scaling my parts to correct for the offset. The offset appears to only occur in the XY axis, never seems to happen in Z though

Example: 
In the part modeled I had the width designed to be 35 mm (face to face, parallel walls). It doesn't seem to matter what size of part I have the final dimensions always seem to be off by about the same amount.
Yup that is what happens. It is simply the plastic cooling and shrinking. It will happen on just about any printer. 0.3mm on a what 40mm part. That is 99.3% on target. 

There are some great blog links about it, 
and here is a Stack overflow where I talk about it more in detail.

The only mitigations I can think of is
1) use a hear chamber.
2) use a SLA 3d printer.

I wouldn't worry about it. Just make sure your designs have good tolerances.