My betas (every 48 hours) have been: 350; 760; ~1260; 2160. I went in for an u/s this morning and it's not ectopic - Thank Goodnes! Unfortunately, that hasn't stopeed me from worrying. An ob friend said that it could be a sign of a blighted ovum. I'd love to hear some stories from folks that had this situation and went on to have happy healthy babies!!
TTC #1,
IUI #1: December 2008 - BFN
IVF #1: Microdose Lupron - July 2009; only got 1 egg; BFN
IVF #2: Natural IVF - Sept 2009; BFP!; D&C Nov. 2009
IVF #3: Natural IVF - ER: Feb 4, 2010 - 1 "M2" egg retrieved; ET: Feb 9; Beta#1 (19dpo): 2567; Beta #2: 6933; BFP w/ singleton w/strong hrtbt! DS born October 2010
TTC#2
IVF #4: Natural IVF - ER: Nov. 20, 2011; ET: Nov. 25, 2011; BFP! Beta#1 (19dpo): 1918; Saw hrtbt on 12/28/11!

Re: Anyone have successful pregnancies but betas that didn't quite double?
I did not have this situation, but 48 hours is not the cut off time for beta doubling time. It is 48-72 hours.
Try going to www.betabase.info and you may find reassurance there.