Man, I've talked about this SO MANY TIMES, including to some of you asking questions here and now.
Callie ... again ... percocet and oxys are THE SAME DRUG.
Here:
Suboxone.com - Understanding Opioid Dependence
Poke around, lots of good info there.
Here's the two minute version: buprenorphine is an long-acting partial opioid-agonist drug used to treat opioid-dependent patients. It strongly binds to the body's opioid receptors (thus preventing withdrawals), even more strongly than full-agonist opioids/opiates (such as heroin, oxycodone, etc, thus rendering these drugs useless when taken while on bupe) but it doesn't activate the receptors very much (hence the 'partial' part) so it doesn't create any noticeable 'high'. You very much feel 'normal' while you're on it. It does act as an anti-depressant, yes.
So, bottom-line, it's an opioid, so YES there are withdrawals from it. People stay on it for wildly varying lengths of time. From a week to years. Just as with any opioid/opiate (the distinction between these terms is academic, btw), the LESS of it you have been taking recently when you QUIT, the LESS your withdrawals will be. The withdrawals from it tend to be considerably milder than those from full-agonist opioids, but they also tend to linger in a mild form for a bit longer.