I also hear great things about the Kahr PM-40 and the Smith M&P Shield. I think the Kahrs go for a little more than a Glock, but you're in the ballpark at $550.
The first thing the OP needs to decide is if he wants to carry something single stack or double stack. A single stack handgun will be slimmer, more comfortable, easy to remove while still in the holster, and can fit a wider range of apparel. A double stack handgun will have more rounds and with the proper holster it can be comfortable, but when you strap this thing on, you're making a commitment to wear this gun/clothes combo for the rest of the day. Then again, all of these suggestions have to do with inside the waistband carry (IWB). Any other method will have other tradeoffs. This is a decision you'll have to make...
If you wish to go single stack, I have a Kahr CM9 and I love it. It is dimensionally identical to the PM9/PM40, but costs a couple hundred dollars less. If you wish to get the same caliber, I would go with the Kahr CM40. The M&P Shield 40 is also a great choice but finding one right now may be a bit difficult. Still, I recommend it.
For double stack handguns, I think the best compacts (^those up there are subcompacts^) are your basic 4 from well-known companies. This would include S&W, Springfield, Glock, and Ruger. I carry a Ruger SR9c daily and it is very comfortable in my White Hat holster. Dimensionally, this gun is about the same as an M&P40c, SR40c, Glock 21 (not positive of this number), and XD40 compact. There are slight variations with each one, but each one brings reliability, usability, and dependability to the table. The next question to answer would be: Which one feels best in your hand?
I would go to a gun store and feel each one and see what you think. Did you have any specific handguns in mind?
This post was edited on 1/13 at 10:58 pm