Obviously 6 weeks 6 days is way too early for me to be buying one. So when is a good time and how early did you hear your baby's heartbeat? Also, what brand did you use?                
                First BFP  April 2011, EDD 01/11/11, MMC June 20, 2011 D&C June 20, 2011
Second BFP September 23, 20011 CP diagnosed September 26, 2011
PAL/PGAL welcome 
 
Re: Talk to me about dopplers
I think the vast majority of women here who have a doppler bought the sonoline B. If you shop around you should be able to get it for around 50 dollars. I have never had a problem with mine and would definitely endorse it. It was money well spent for sure.
I started trying around 9 weeks but didn't find the baby until 10w2d. After that I used it every few days until around 20w.
DD born 4/3/10 BFP 4/9/11 missed mc @10w4d- forever loved
BFP 8/21/11 EDD 4/29/12
TTC since 05/10
Dx: PCOS,Hypothyroidism, Endometriosis, elevated prolactin
Surgery: Laproscopy 12/15/11 to remove Endo, 8/12/11 to remove 7cm cyst and cauterize 4cm cyst
April 2011 - Clomid 50 mg round 3 - O'd CD 18 BFP 5/2 C/P 5/10
RE Consult 06/02/11, Sonohystogram - clear, DH SA - great! HSG all Clear.
Meet up with RE for plan of attack 10/25: 2 natural rounds and then onto clomid
CD 21 BW shows poor ovulation, November 2011 Clomid 50 mg round 4 - BFP on 11/30
I have the sonoline A. The B has more bells and whistles, but I didn't feel like paying an extra $20.
I found it in the 11th week. It was 50/50 between 12-14w, and I could always fint it after 14w.
BFP #3 via cancelled IUI ~ C (2lb 3oz; HELLP) 5/16/11
BFP #4 via the natural (free!) way ~ E (8lb 11oz) 9/13/12
Someone posted they heard the heartbeat using the sonoline B at 8 weeks. I just ordered mine yesterday and ordered the 3mhz as opposed to the 2mhz because the 3mhz is more sensitive and able to detect the heartbeat earlier on. They were the same price. I ended up paying around $54 for mine and did the expidited shipping so about $62 total. Mine is suppose to arrive on Monday and I'll be 8w5d, so we'll see if it works. I'm sure I'll be exploding on this board if it does.
BFP #3 11/27/11, EDD 8/3/12
BFP #1 8/1/11, Natural MC 8/12/11 6 weeks
BFP #2 9/25/11, Natural MC 10/3/11 6 weeks