Although, for the most part, I have been lucky with the treatments I have had via Groupon I would really recommend checking online reviews of the salons before buying vouchers
At the weekend there was an offer in London for Microdermabrasion. I didn't buy the voucher as I wanted to assure I was able to have the treatment as it stated on the offer info that it wasn't recommended for acne sufferers. I went to the clinic and it was really shabby looking so I decided to check the reviews onlne before booking and was alarmed to read some really terrible reviews including one where the lady was taking legal action to get her deposit back because they had given her false information and also stating that the clinic had failed the Healthcare Commission Inspection. Needless to say I've not booked it which is a shame as I have wanted to try this treatment for a while now.
Here are the reviews I've read (I suspect the 9 and 10 star glowing reviews were added by friends and family as they are very different to the opinion of the majority of reviewers)
www.wahanda.com/review/place/pasha-clinic-north-london/1725/
www.allinlondon.co.uk/livelistings/review.php?ail=46308