I don't use those tubes myself but my mom has bought them before. Those plastic tips work fine but did you know that you can use the regular wilton tips with those tubes? You just need to screw them on with the coupler rings...Then you have the freedom of using whatever tips you want instead of having to use one of the only 4 plastic ones that are available.
Personally I think the tubes aren't as easy to pipe with. They just feel weird, but then I'm use to the bags.
If it is a one time thing you might like them, but if you are going to be making alot of cakes, I think the Wilton tips are the way to go.
When I used the store brand icings, I had alot of problems with air bubbles and you really can't control it.
You can buy b/c premade:
http://www.countrykitchensa.com/catalog/mini.aspx?T=1&SubCatId=1013
Icings of all types:
(From sugarcraft.com)
http://tinyurl.com/22a27h
HTH
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