Long lens - I wanted to get something longer then my current 28-200mm. I ended up finding the Phoenix 650-1300mm f8-f16. It was ~$300 from bhphotovideo.com (great people, good prices, I will be purchasing some pro lenses from them). The UV filter was another ~$80! I have had it for around a month now and have had an opportunity to work with it a good deal. Overall I like it, but it does have many problems, about what one expects from a cheap lens.
Note I am using a 1.5x crop factor sensor so the lens is more of a 975-1950mm f8-f16
-A large tripod is needed. The lens weight 4.4 lbs so a small tripod will not cut it. When dealing with a lens that is that long (really more of a small telescope) you are going to notice every little shake, unless it is absolutely still.
-Those slow f stops are amazingly slow. The light gathering ability is very poor which hurts how much you can cut down the shutter speed.
-Chromatic aberration is noticeable. Yes this really does harsh things to your final image, but you really are getting what you pay for.
-I have always used auto focus lenses this manual focus thing is new to me. It is tough because the image in the viewfinder is dark (because the lens does not send much light through)
-Focus OK I should have known this from when I took optics in physics, but when they say a focus distance of 16 feet they mean 16 feet at 1300mm. I am not sure what it is at 650mm but it is a good deal further out (30+ feet)

With the combination of trying to minimize the shutter speed and the slow f-stop one ends up with a lot of dark images. Photoshop CS shadow/highlight can help you a little bit here, but the images are still dark.

OK so that was the bad. The good is: look at some of the below images. The ones of the deer are all taken from 50-70 feet away, with none of the images being trimmed or blown up. The lens was not even at 1300mm! The Owl was a LONG ways away and I was able to fill the frame head to tail. I even hand held the lens while photographing the owl. But the lens is long and heavy. Left arm all the way extended to keep my hand on the focus and most of the weight is at that end. One needs to be fairly strong to be able to hand hold this lens.

Like I said, overall I like it but there are many problems. It has enabled me to get images that there is no other way that I could (ya sure you sneak up on the deer in crunchy snow).