Yes, it's worth it.
For your second need it's not going to be great, but that's just bookmarking in general. They're fairly 'weak' as far as backlinks are concerned, but it's great for getting web pages noticed and indexed.
If you're trying to get less quality pages indexed it will take a lot of bookmarks across a lot of bookmarking sites, so be sure to have a ton of emails ready for you to start creating accounts with. (seriously, at least 100 emails just to use for creating bm accounts.)
The more accounts you have the less chance you'll have of seeing those accounts get banned by the bookmarking sites. If they do get banned, don't worry, it's no hardship to create more (i have over 1500 accounts and running...)
It will run on your home machine just fine, but make sure you have a good set of private proxies. Forget the scraped proxies, private proxies will be worth the investment.
It has a feature called RSS camo - watch the videos they provide and set that up properly.
When doing submissiona, I try not to let any one bookmarking account have more than 2 submissions per day, but that's usually not a problem if you have a load of accounts. (depending on just how many submissions you're actually going for)
Captcha's are annoying!
They only offer 2 services, and the other service to decaptcha is way too expensive!
Decaptcha themselves are pretty shite, but what can you do...
I've had 20% higher success rates with manual entry everytime, but it's just so tedious you just have to go with a captcha service.
Overall, it's worth it if you have a good strategy behind what you'll be using it for.