I think the thing about Link Farm Evolution, is that it's not for noobs.
The more you use it, the better you will utilize it. This is because you will sort through the sites the work and don't work therefore making your submission approval rate increase.
And it would be very hard to get banned using LFE! If you use the hooks, it's going to fetch random content for EACH site, so therefore each on your blog posts are somewhat unique.
So LFE is definitely worth the price. If you know what you are doing you can get your WPMU blogs indexed very quickly by using the Pligg tool in LFE.
And like 99.9%
SEO tools on the market, your not going to see the results overnight. I think this is the thing most noobs don't get.
SEO isn't something you do in 2 minutes flat and then think its finished.
But overall, if you actually want to use your investment wisely, you will quite easily make a nice ROI