I know you are looking for the opinions of practicing RN's but, I feel that I can contribute something to the answer you are looking for. I am graduating from a three year diploma RN program in Ontario and can at least communicate my hours spent in clinicals and preceptorship and how I believe this has prepared me to work as a graduate nurse (take provincial boards on June 9th).
1st, 2nd & 3rd semesters - 16 hours per week
4th & 5th semesters - 20 hours per week
6th semester (entirely preceptorship, no classes) - 600 hours total (in other words, working full-time 12 hour shifts nights & days with an RN 1:1 on her rotation)
I will be done my 600 hours on May 2nd. Do I think I am experienced enough to be the perfect nurse? No way. But, I do have enough experience to be competent. To me, competency means providing the best, most appropriate care possible, following the CNO guidelines (our governing body in Ontario), following policy and procedure in the hospital I will be working in as a GN and as an RN, and RECOGNIZING when there is a problem beyond my abilities and seeking the help of someone more experienced than I.
Did my 600 hours prepare me to be a GN? Yes and no. There are always those nagging doubts that you are able to perform the job. If I didn't have doubts, THEN I would be a danger to my patients. Experience only comes with time, we won't be as competent and capable as a nurse with ten years of experience until we HAVE ten years of experience. Seek out the advice of an experienced nurse if you aren't sure. I have personally found that EVERY nurse I have encountered is willing and happy to offer their expertise and assistance. This is one way to make the most of your clinical hours - ask questions! Ask lots of questions! Another way, is to always be ready and willing to attempt ANYTHING within your scope of practice as a student! If you are willing to do the less desirable jobs eagerly and without reservation, the nurses will respect that and they will look for you when they are doing something unusual or requiring more skill. Even if you can't physically participate, they will let you help in some way (like being the recorder during a code). The experience is invaluable. The harder you work, the more the nurses will want to help you. If you have a slow time in your day during care of your own patients (like your patients are all independent and it's lunch time), offer to feed someone else's client for them, restock the linen carts, restock the med carts, restock the med room, restock the IV trays. Keep busy, busy, busy.
Nightshifts are a wonderful time to learn. If you have done everything you can do on the floor and there is a lull in activity (there typically is two to three times per night - this is when most of the nurses congregate at the desk and do all of their charting, check orders, update nursing care plans, double check that requisition slips for tests have been sent to the lab or diagnostic imaging, etc), read the policy and procedure manual - if you have already read it, read it again. You can also spend time in the clean and dirty utility rooms just going through the carts and cupboards so that you will get an idea of where things are. Talk to the doctors too. I have met so many doctors who LOVE to teach. One surgeon explained the exact procedure for a vaginal hysterectomy - OMG, I have a much greater understanding of the pain and discomfort the client experiences post-op.
Just always do your best and always be ready, willing and able to help. If you make a mistake, OWN your mistake - admit it and learn from it. Those are the best ways to make the best of clinical time that I know of. Good luck and the nursing profession will be lucky to have you (I know this because you asked this question, it demonstrates that you WANT to succeed and you WANT to be a nurse).