I have used Uniconnect for 18 days while I was in Europe last year. The service was very good, the cost very low. I used it only for incoming calls and for outgoing I used Matrix and when I got the bill, my wallet burst - around 25k. Since Matrix had already taken my credit card authorisation, there was nothing else to be done. Uniconnect was a prepaid one with full incoming free across Europe and UK. Matrix had incoming free only in UK, whereas Europe incoming was chargeable.
This year again I used Uniconnect and Clay when I went to Malaysia and Singapore. The same story repeated - Uniconnect this time was postpaid with full incoming free across Malaysia and Singapore, the bill was a super measly Rs 20 only.... Yes, you read it right - only twenty rupees and that too for calling my Clay number once in Singapore. Clay was a super disaster like Matrix - they charged me rental plus access fees for free 30 minute per day calling to India (then how they call it free) and the total bills were for around Rs 10k. I contested the rentals and access fees and they waived the rentals for about 2k and I eventually paid up Rs 8k in all.
These are my experiences. For me, Uniconnect was very good with superb services. No call drops anywhere. Only thing they did not provide was GPRS/3G facility which they claimed will cost a bomb and hence they refrained from providing.
My sister used Matrix when she travelled to US for 20+ days, again pretty same disaster story - she was charged ard Rs 22k. She did not contest and she paid up, swearing never ever to touch Matrix again. She went this month to Thailand and she bought a local SIM there.
Travellers/readers here may just read the above for guidance and information. They are free to take any provider. What may be food for me may be poison for someone else. Matrix and Clay may have been very bad for me, but for others, it may have been very good. Similarly Uniconnect also.
BTW, the website address for Uniconnect is Uniconnect.in.