IMO it's not a terrible option if you have a smaller dog (read: not a GSD) and need a guerrilla set that you can carry around, set up in a public space, and collapse for storage. Even then, if you're going to get serious about actually doing agility (vs. just training the obstacles as casual tricks for fun), you'll just have to rent training space or borrow a friend's setup, because you can't duplicate serious training on that set.
If you have enough space for real agility equipment, and know you actually want to do agility, then definitely go with real equipment. But if you're just looking to dabble and want to play around with stuff for fun, then it's not the worst way to drop some money.
I'd look at it more on the level of the goofy "training aids" I pick up at the dollar store, though. Not serious sport equipment, just stuff for fun.
ARCHMX TDCH Pongu the Insane, CD-C, RN, RL1X5, RL2X4, RL3X2 (GSD mix, b. Apr 2010)
Crookytail the Tigerwuff, RL1, NTD (Akita mix, b. Jan 2011)