Group Buying Sites: The bad and the good (experiences)

Now I'm not sure if I'm really getting good value from these group buying sites.  I'd rather buy from reputable merchants next time to save up on emotional trauma.

BAD: 
Metrodeals.com - D`Spa and Skin Center (Room 1508 Amorsolo Street cor Dela Rosa Street Legaspi Village Makati City)

I was led to a small, cramped room with dirty sheets and towel on the recliner.
The skin treatment, supposedly worth P1500 which I bought for P175 didn't even seem worth more than P50.  I looked at the machines inside the room --- everything was so dirty and the ultrasound gel bottle I saw on the table was a bit muddy. 
The "therapist" didn't look so credible.  She sang out loud while she was doing the treatment and was chatting with the other employees from the next room as she went about her business.

GOOD:
DealGrocer.com - Lisa Macuja Swan Song Series
My husband and I bought Lisa Macuja Swan Song series tickets from Deal Grocer. We were very happy coz they were so organized.  They had a separate line and reserved seats for Deal Grocer voucher holders.
No headache there and the shows were great!

BAD: 
Ensogo.com - The Beauty Room/Embassy Spa Manila Pavilion Hotel

My appointment for treatment was at 2PM afternoon. I arrived at 1PM to make sure I don't miss my appointment because Malate is really far from my place. At 3PM, the doctor hasn't arrived yet.  It was already an hour after my set appointment so I requested the receptionist to call the doctor to check if she's near. The doctor was caught in traffic, she said.  I was really upset and asked if I can talk to the doctor (Dr. Christina V).  The doctor wasn't apologetic and even had the gall to ask me, "Why were you so early?" I got mad at that point and demanded for an immediate refund.  Which they did give me actually, (even if it's not the usual policy) probably because my face was red with fury.

I guess the key learning is to carefully select the deals from these sites.  Do not buy from unknown merchants.  And be careful with your credit card details.  It might be better to pay using paypal or bank over the counter systems.  I read a lot of payment horror stories.

Now, what do I do with my remaining vouchers?