Hi all! I have spent countless hours reading all the brilliant info this forum provides since buying a Pentax K100DS. If you want a laugh, prior to jumping into the Pentax and SLR realm, my previous camera was a Toshiba PDR-3300!
Back to topic however. I know that the Tamron 70-300mm has been around for quite some time and has been discusses thoroughly here and elsewhere. The more I have been using my Tamron 70-300mm AF 4-5.6 "Macro 1:2", the more I think that there must be very few lenses in existence that can give you such value for your money!
The macro capability is great at 1:2 it is one of the closest focusing zooms you can have. Getting the 1:2 magnification from a decent distance away is a positive if you are trying to photograph subjects that will run away on you if you get too close. Also, search these forums, and there are a number of great 1:1 or better macro shots taken with this lens using the Raynox 150 or 250.
Photozone and other lens reviews show that it has quite a decent level of IQ as well compared to the Pentax 50-200mm and 55-300mm lenses.
For $125, it is tough to think of another AF zoom lens that can match this one for it's performance.
Despite my amateur skill level, I am able to take close up's, hand held:
And get shots from a distance for situations (ie. water, or tricky subjects) as well: