What ranges are you planning on using it? Are you going to compete with it? Type of competition? For stuff under 200M, I generally prefer the EoTech. The Aimpoint CompM family is also good but the problem is, neither sight offers any internal magnification, so they're not so great at longer ranges. You can buy extra, external magnifiers, but you're adding additional weight and bulk to your rifle. If you plan on shooting at longer ranges, an ACOG or Elcan might better suit your needs. However, the former isn't the best for CQB distances and the latter is relatively heavy and early versions had problems with their mounting system.
For general fun, plinking and paper-punching out to 100M and sometimes out to 200M I prefer the EoTech, although the Aimpoint is a close second!
For those in the know and have the scratch, the S&B ShortDot seems to be the cat's ass, but for most of us, just a little hard to justify unless we're deploying to Afghanistan and our arse may be on the line!
If you're just looking for something to use for occasional plinking and/or the look cool factor, there are several Chinese knock-offs around for a fraction of the price and actually stand up to a suprising amount of abuse. Nowhere near the quality of brand names, but not bad considering the price. Bushnell is also offering an ACOG lookalike in their Trophy line that seems to be okay, especially since it costs about $1000+ less than an actual ACOG.