How do you feel about macro extension tubes?

[mario8402]

I would like to start taking some really close up macro pics, but I do not have the cash at the moment to shell out 900 for a decent macro lense so please do not give me that lecture. I am considering cheaping out and buying some extension tubes from ebay.. 20 bux or so wont break the bank so we will see.
I basically want to hear from the people that use these, are they worth it? Which ones should I get? Maybe post a pic that you have taken in macro using the tubes/filters and also a link to where you bought them from. I am shooting with a D40 with stock lense 18-55mm

Here is what I am looking at
This one is cool because it comes with a tripod. Kinda confuses me though because it doesnt have a tube, just a filter looking lense:
http://cgi.ebay.com/MACRO-Close-Up-...yZ106860QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

No tripod, just lense filter looking ones
http://cgi.ebay.com/Macro-Close-Up-...ryZ43479QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


This one has the filter looking lenses and also an extension tube:
http://cgi.ebay.com/Extension-Tube-...ryZ29982QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


too expensive:
http://cgi.ebay.com/5x-Macro-Extens...ryZ43479QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

[BlueCorn]

Tubes are just spacers. There are no optics.

http://www.reefcentral.com/forums/showthread.php?s=&threadid=1340707