Actually, I wouldn't spend $150 on a red dot...there are several out there that will work fine for around $100 ...but the next big step in quality is around $300 or so (Aimpoint Comp C, Bushnell Holosight, etc).
About the only thing in the $150 range is the Ultra Dot. I have no exerience with them, but I've heard good stuff about 'em. They've got a 4 dot version, but it's pushing $200.
there is a VERY long thread about the TacPoint...you might want to read the last 5 pages or so. It's a clone of an Aimpoint, that *seems* to be doing okay for most people. I was gonna get one, but then everyone was out of the model I wanted. I just got a Simmons Shot Dot, a little 4 reticle dot sight for $65.
A buddy was over last night, and he wanted the sight for his rifle that I built him...so I sold it to him for $60 and snagged a Holosight off the EE for $ 160.
There's another one there for $200, which is a little high for a used one, imo...I can get 'em new for $223 dealer pricing at Midway. $160 was a great buy, though, so you may just want to keep an eye out on the EE for another Holosight, or an Aimpoint Comp C.