Are purge walls worth it?

I've recently been able to print with dual extrusion for the first time thanks to the new Flashforge Creator Pro at my job. I discovered Makerware's purge wall feature and was wondering what others' experience has been like either printing with or without the purge walls. On one hand, I can see how it's useful in creating a nicer print. On the other hand, it does seem to waste a lot of time and material, plus it seemed like it made the actual printed object smaller than how it appeared it would print when viewed in Makerware.

Is it worth it to use purge walls? Are there settings that will still work but waste less time and material? Is there a good alternative to purge walls? Just curious what others think.

I'd say don't use purge walls if there is a working alternative. They definitely make dual extrusion a much longer and more expensive option.
The latest version of simplify 3d has a thing called a cleaner column (something like that anyway) which sounds like a much better option.

When I get round to serious playing with dual extrusion I'll give it a go

I have found that a good way to do clean bicolor prints easily, is to turn off the unused hotend. That has a few advantages :
1/ the cool hot end is slightly shorter than the hot one, which reduces the chance of hitting the print with the unused head.
2/ there is no oozing
3/ if the 2 colors are on different Z planes it is not making you lose too much time.

I do that with M104/M109 codes placed on the tool changing scripts. In S3D it is quite easy to setup in the different processes.

However it is admittedly less interesting if the 2 colors are intertwined in a complex way. It is efficient so it might still be interesting for small high quality prints.

The purge tower is a good bet for the taller prints but I haven't tried it just yet either.