Nimbec, when are you starting the injs? Are you on the antagonist protocol or the agonist?.. I guess with the mild pcos, u wont be under stimmed, infact you could respond well.
I do not have pcos, and so was put on the antagonist protocol... my RE is a really patient and understanding person, but I suppose she got too greedy to extract more mature eggs

and me stimmed for 12 days. Luckily for her, she got 8, all mature, mission accomplished. DH's SA came back fine, everything looked so rosy, she insisted on standard IVF rather than ICSI. Alas!.. only 3 fertilized and 2 made it to day3 with grade-B. At this point she became conservative and hesitated to let them progress upto 5th day, so froze the remaining 2 on day3. So much for "lateral impression" of my eggs and DH's sperm!...
Then I had a detailed discussion with RE and she told that, my eggs had some amount of SER (some morphological anomaly, which may or maynot affect implantation and pregnancy.. let me not go into tmi, as its already a long post..), due to which the eggs could not fertilized normally through IVF (so ICSI cud hav been done!.. but late realization..). She told that many donor eggs also have it, but REs dont take it so seriously, bcoz SER eggs do produce healthy babies.
Apparently, its the healthy eggs that may progress to have SER before ER, if ur stimulation is longer, and increases 3 times with a short protocol / antagonist protocol. So usually only long protocols are suggested for patients with pcos or those who had an instance of SER in previous ER.
This was a lot of blah blah... My case was a late realization, but I hope this info is of some use to people with PCOS or SER+ cycles, and I hope RE's know well, and suggest appropriate protocols on a case-to-case basis.
Libby, as far as my experience goes, I didnt have any negative side effects other than having really heavy feeling bbs and sore nips. And I guess I put on a pound or 2 extra, but cant be so sure to attribute the weight gain to the stims...