I just picked up a bike jersey on ebay, but am concerned that it might be a smidgen big. I figured bikeit would be a good place to ask for opinions. My main concerns are that the material, although synthetic, aren't really tight fitting. That is, they don't cling to the body like underarmor, but are loose, although slimming. Likewise, the sleeves don't cling to my upper arm. They are close, but a bit to big to actually necessitate the elastic. Thoughts?
Edit: I am not racing, but I am biking xc mountain and road cycling about 4-6x per week.
Only you can decide how you want your jerseys to fit.
That being said, the MTB crowd generally prefers a looser fit, and the roadies prefer tighter clothing IME.
Unless your speed requires aerodynamics, comfortable fit is more important than tight fit. Hence, redcon1's comments above ^^^. For road riding, it's usually better not to have fabric flapping in the wind.