I haven't managed to get yousaytoo to accept hubpages, its better for publicising blogs. They all work as part of a backlinking strategy, although whether they are worth the time rather than putting it into hubpages I'm not sure. They most definitely help, but in the time I have devoted to them and others I could have written at least another 10 hubs!
Redgage is definitely worth it as it only takes a couple of minutes to add a link to your hub, Xomba only requires 150 words for a bookmark, so that's not too time consuming, however Shetoldme should be around 250 words, which takes a little longer.
If you use them, add in the relevant info straight after you have written and published your hub, whilst the topic is fresh in your mind. You should be able to rattle through all of them pretty quickly then.
The best bet is to set up an account on each, and try it out with a couple of hubs which are already generating some traffic to see if it works for you. If it doesn't, don't waste your time - if it does - go for broke!